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No) PREFACE

Here is an important Resolution pertaining to the Proposed AGS Diamond Grading Standards. The Diamond Standards Manual was distributed to AGS member firms in April 1966. The Resolution was adopted later the same month.

It is important that you read and be guided by information in this Resolution. It governs the manner in which the proposed standards may be used by member firms.

American Gem Society

RESOLUTION

WHEREAS, the best interests of the American Gem Society require that use of the Proposed Diamond Grading Standards be subject to regulations which will insure the integrity of the Standards; and,

WHEREAS, permanent rules for compliance should be developed through the experience of the Society and its members using the Diamond Grading Standards; and

WHEREAS, it is the responsibility of the International Board of Directors to establish policy for the guidance of the Society's membership; now therefore,

BE IT RESOLVED that the following temporary rules will apply to use of the Proposed Diamond Grading Standards:

1. Use of the Proposed Diamond Grading Standards shall be voluntary; the Standards may be applied to all or any part of a member's diamond stock, and unmounted diamonds examined for appraisal.

2. All representations of compliance with the Standards, or correlation of these Standards with another diamond description or grading system, must be accurate and true in fact, and responsibility for such accuracy shall rest upon the individual member.

3. These Standards may not be represented as the "official" standards of the American Gem Society until the Standards have been approved and adopted by a vote of the Society membership.

4. The Diamond Grading Standards may not be mentioned in any advertisement in any media, including newspapers, television, radio, direct mail and brochures.

5. Members shall not, in offering diamonds for sale to non-members of the Society within the trade, state or imply that such diamonds have been graded in accordance with the Proposed Diamond Grading

Standards, nor shall they make any reference to the Standards in advertising or promotional material, nor on diamond papers, memos and invoices supplied to non-members within the trade, nor in correspondence with non-members within the trade.

6. Any diamond labeled or described as conforming to an AGS grade must in fact have been graded, while unmounted, in accordance with the Standards, by a competent AGS member.

7. The AGS diamond grading symbols, whenever applied to a diamond in written or verbal form, must be presented completely, and in the prescribed order.

AND BE IT FURTHER RESOLVED, that the International Board of Directors shall consider any violation of these rules to be detrimental to the best interests of the Society, and will, accordingly, recommend to the International Admissions Board the termination of the membership of any member who violates these rules;

AND BE IT FURTHER RESOLVED, that a copy of these rules, and of all amendments and additions thereto made by the International Board of Directors, shall be supplied to each firm member and individual member of the Society.

Approved:

April 22, 1966

Board of Directors Atlanta, Georgia

American Gem Society

(Instructions: After reading, file this at the back of the Diamond Standards Manual.)

PROPOSED DIAMOND GRADING

STANDARDS

Prepared by the

AMERICAN GEM

SOCIETY

INCE THE LATE 1930's the American Gem Society and its membership have taken a keen interest in all aspects of the grading of diamond quality. The Society and many of its individual members, in association with the Gemological Institute of America, have developed the instruments and techniques which are essential to the accurate and uniform grading of diamonds.

Among the most significant developments in diamond grad-ing equipment have been:

1. The AGS Diamondscope®, in 1937. This binocular micro-scope with a specially designed dark field lighting sys-tem has been repeatedly modified and improved. Used primarily for clarity grading and the examination of the interior of diamonds, it is useful also in examining the details of finish, and present day models are equipped with accessories for determining cutting proportions.

2. The AGS Diamond Colorimeter, in 1941. This optical-mechanical instrument measured the fine nuances of body color in a diamond, and became a practical yard-stick for diamond color grading.

3. The color graded Master Diamond Sets. Sets of dia-monds of differing color grades, owned and maintained by AGS members, are individually graded on the Col-orimeter in AGS Headquarters. These Master Diamonds are used for comparison grading of other diamonds.

4. Diamond Proportion Screens. Adapted to several dif-ferent projection devices, this Screen permits a direct reading and grading of a diamond's proportions and major symmetry.

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5. Specialized measuring and computing devices. Several devices, like the Leveridge Gauge, have simplified the once difficult task of measuring the separate parts of a cut diamond and analyzing those measurements.

6. The AGS Electronic Diamond Colorimeter. Developed in 1955, these instruments ( unlike the earlier colorimeter which was a single instrument maintained in the Socie-ty's offices) are leased to AGS member firms. They per-mit accurate, uniform, and reproducible measurements of a diamond's body color. ( Master Diamond Sets, see #3, are now graded on the Electronic Colorimeter in Society Headquarters. )

7. Diamond Clarity Comparison Photographs and Dia-grams. These photographs and diagrams are presented for the first time in this Manual. They provide the first tangible printed yardstick for the measurement of dia-mond clarity.

Availability of this equipment has made it possible for prop-erly trained jewelers to grade the CUTTING, COLOR, and CLARITY of diamonds with a high degree of accuracy and uniformity. Yet, prior to publication of this Manual, little had been accomplished in the jewelry industry towards standard-izing diamond grading procedures and nomenclature.

Over the years a number of jewelry concerns have established excellent diamond grading systems and meaningful termi-nologies of their own. On the other hand, some "private" systems are confusing and deceptive. Of the traditional trade terms —"Wesselton," "VVS," "fine make," etc., only the high-est grade of color and the highest grade of clarity have been acceptably defined; yet those grades represent only a very small percentage of diamonds on the market. Other tradi-tional terms have become virtually meaningless because of wide-spread misuse.

Therefore, with the publication of this Manual the American Gem Society seeks to achieve standardization of diamond grading among its own membership — a significant segment

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of the American jewelry industry. Diamond Grading Stand-ards will establish a basis for understanding between the AGS jeweler and the diamond purchaser. They will afford protection for both the buyer and the seller by spelling out the various aspects of diamond quality and value, and by providing a strong framework for fair competition.

The Diamond Grading Standards presented in the Manual are the results of more than 10 years of work by the Society's Diamond Standards Committee, a committee composed of diamond cutters, retailers, and educators. The individuals most active in this program were: William Baumgardt; Carle-ton G. Broer, C.G.; G. Robert Crowningshield, C.G.; James G. Donavan, Jr.; Thomas Gorman; Leo Kaplan; Richard T. Lid-dicoat, Jr., C. G.; Robert Limon, C. G.; Darwin Neumeister, C. G.; William Preston, Jr., C. G.; George Sloan, C. G.; and Alfred L. Woodill. The photographs for the Clarity section were taken by Mrs. Jeanne G. M. Martin of the Gemological Institute of America.

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AMERICAN GEM SOCIETY DIAMOND GRADING STANDARDS

Scope and Application of the Standards

The AGS Diamond Grading Standards provide a numerical description of a diamond's quality and value factors. Follow-ing the procedures detailed in the three grading Sections of this Manual, a number of 0 through 10 is applied to each of the factors, CUTTING, COLOR, and CLARITY. Represent-ing the highest grade is 0, with 10 representing the lowest grade. Weight is expressed in metric carats to the nearest 0.01 carat. The four figures are expressed in the order of CUTTING, COLOR, CLARITY, and CARAT WEIGHT, preceded by the words "AGS Grade."

1. A round brilliant-cut diamond, correctly cut, colorless, and flawless, weighing exactly three-quarters of a carat, will bear this description —

Rd br AGS Grade 0/0/0 — 0.75 ct

2. A round brilliant-cut diamond which is correctly cut, grades 2.25 on the AGS Electronic Colorimeter', has the tiniest sort of inclusion, and weighs exactly one and one-half carats will bear this description —

Rd br AGS Grade 0/3/1 — 1.50 ct

3. The designation of "AGS Grade 7/1/8 — 3.46 ct" would describe a diamond which has serious deficiencies in cutting, has fine color, and exhibits large, or numerous, or dangerous inclusions and blemishes.

The individual Sections in this manual on CUTTING, COLOR, and CLARITY define each numerical grade and give detailed instructions for the application of these grades to a diamond. *A Table, Page 30, is used to convert the Colorimeter reading to the AGS Color Grade.

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Grades of CUTTING are defined in terms of the degree of departure from ideal proportions and finish.

Grades of COLOR are defined in terms of the degree of departure from a colorless body, as measured by the AGS Electronic Colorimeter.

Grades of CLARITY are defined in terms of the degree of departure from a complete absence of inclusions and sur-face marks, when the diamond is examined by a trained and experienced person employing binocular magnifica-tion of 10X with both dark field and direct illumination.

Tolerances are specified for each grade of each factor. Tolerances are narrower in the higher grades and broader in the lower grades, as indicated by diagram, Fig. 1.

01 2 3 4 5

6

7

8

9

10

Fig. 1 The theory of diamond grading demonstrated in Fig. 1 applies to each of the quality factors, Cutting, Color, and Clarity, although the diagram is not an equal represen-tation for each of those factors. Notice there is room for differences in two diamonds of the same grade. For instance, in the color of two diamonds in Grade 5, one might be noticeably more yellowish than the other. How-ever, the latitude is less in the higher grades. Also notice a greater difference between such grades as 6 through 8 than between grades 0 through 5. The greatest differ-ences will be noticed within grade 10, which includes all cut diamonds, below the grade of 9.

This Manual, together with official additions which may be made from time to time, comprises all the provisions for application of AGS Grades to diamonds. An AGS Grade may not be applied to any diamond unless that diamond has in

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fact been graded by a competent AGS member in accordance with these Diamond Grading Standards.

The Manual does not provide a study course in diamond grading. It is intended to be used as a guide by those whose study and experience have already developed their diamond grading skills.

Employment of the AGS Diamond Grading Standards in advertising, selling, grading, and appraising diamonds im-poses on the AGS member the obligation to apply the AGS Grades in the prescribed order and with conscientious con-cern for accuracy.

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SPECIAL NOTE ON THE FIRST PRINTING At the time of the first printing of this Manual there remained several unresolved problems concerning details of "ideal" cutting of fancy shape diamonds. The Diamond Standards Committee is continuing to work on this matter, and an early solution is expected. As soon as the new material on fancy shape diamonds is available, copies will be furnished for all Manuals.

Pending the publication of this material, the following guides may be applied:

CUTTING. The narrow cross section through the diamond should have the same proportions as the ideal round brilliant cut. Major symmetry must be graded as in the round brilliant cut, except where this is precluded by the fancy shape. Finish and symmetry details must be graded as in the round brilliant cut.

COLOR. Color grading methods for round brilliant cut diamonds apply to fancy shapes as well. Grading is done by comparison with Master Diamonds only, since the Colorimeter does not accommo-date fancy shapes.

CLARITY. Clarity grading methods for round brilliant cut diamonds apply to fancy cuts.

CUTTING

I. General Provisions.

Grades of cutting are defined in terms of the degree of depar-ture from ideal proportions and finish. Specific deductions are imposed for each cutting fault or departure from the ideal. The total of the deductions is converted to a CUTTING GRADE on a scale of 0 through 10.

Ideal proportions for the round brilliant cut diamond are those published by Marcel Tolkowsky in Diamond Design ( 1919), as shown in the diagram, Fig. 2. These proportions provide maximum brilliancy consistant with a high degree of dispersion ("fire" ), assuming the light is falling from all angles on that portion of a diamond above its girdle. In Fig. 3 several combinations of incorrect proportions are illustrated.

100%

53%

16.2%

10 to 2.5%

60.3 to 61.8%

Z34f° 34i°

98f° N./

Fig. 2

Angles and proportions of the ideal cut — Tolkowsky.

43 I%

7

F

Fig. 3

Some departures from ideal proportions. "Excess weight" in shaded areas. A. Shallow crown. B. Shallow crown and shallow pavilion. C. Shallow crown and deep pavilion. D. High crown and deep pavilion. E. Small crown angle. F. Large crown angle. There are 26 possible combina-tions of basic proportion faults, incorrect crown height, incorrect crown angle, and incorrect pavilion depth.

8

Major symmetry faults are considered to be proportion faults. The six possible faults of major symmetry are (1) girdle out-line out-of-round, (2) appreciable variation in diameter of the table, (3) table off-center, (4) table tilted with respect to the plane of the girdle, ( 5) great variation in thickness of the girdle, and ( 6) off-center culet. Fig. 4 shows these cutting faults.

C

Fig. 4 Major symmetry faults. A. Girdle out-of-round. B. Off-center culet (very large culet). C. Table off-center. (Considerable variation in table diam-eter in this example.) D. Variation in thickness of girdle. (Caused by huge natural in this example.) (Tilted table See Fig. 13).

9

Upper-girdle facet--rown

Fig. 5

Girdle (enlarged)

10

Fig. 6

Ideal finish for the round brilliant cut diamond consists of the uniform and symmetrical placement of 58 highly polished facets as shown in the diagram, Fig. 5,'with the lower girdle facets extending 13/16 of the distance from the girdle to the culet, with the star facets extending 1/2 of the distance from the table to the girdle, with a polished culet just large enough to resist chipping, with the girdle smooth ( though not neces-sarily polished) and perpendicular to the girdle plane, with no apparent variation in the thickness of similar parts of the girdle, and with crown facets correctly aligned with the pavilion facets. Departures from ideal finish, including faults of symmetry details, are shown in Fig. 6.

Fig. 6 Faults of finish and symmetry details. A. Extra facet replacing junction between adjoining lower girdle facets. B. Pavilion facet open at girdle. C. and D. Faulty alignment, crown and pavilion facets. E. Lower girdle facets of unequal length. F. Lower girdle facets too short. G. Lower girdle facets too long. H. Wavy girdle. I. Extra facet.

11

In assessing deductions for the various departures from ideal proportions and finish, the AGS Diamond Grading Standards for CUTTING have taken into account two things: (1) the beauty of the stone, and ( 2) the degree to which excess weight has been retained at the expense of beauty.

Accuracy in ascertaining and reporting the Cutting Grade is the responsibility of the AGS member who makes use of AGS Diamond Grading Standards. Use of the Work Sheet as shown on page 25 is recommended to assure speed without error and to provide a permanent professional record.

II. Techniques and Instruments.

The procedures for determining the grade of CUTTING are divided into three principal steps: ( 1) analyzing the dia-mond's proportions and major symmetry, ( 2) assessing the finish and symmetry details, and (3) applying the deductions, the total of which is converted into the CUTTING GRADE.

A. Three different methods may be employed to ascertain the proportions and major symmetry of a diamond. Several instruments and specialized devices enable the expert dia-mond grader to complete the task with speed and accuracy.

1. The several parts of a diamond may be measured directly and the measurements converted into percentages of the average girdle diameter.

The screw micrometer, the Leveridge Gauge ( a clock dial micrometer), and the GIA Table Gauge, are used to obtain measurements of girdle diameter, full depth, and table diameter. Fitted with a set-screw attachment, the Leveridge Gauge can also provide an accurate measurement of the table diameter, girdle thickness, and culet size. Crown height, pavilion depth, and girdle thickness may be measured by the Leveridge Gauge with the Crown Height Attachment in place. These last measurements may also be taken by the Leveridge Gauge with the diamond held table-to-culet in a parallel jaw device such as a sliding caliper.

These instruments and their applications are shown in

12

C

Leveridge gauge with set screw. C. Measuring pavilion depth with dia-mond held table to culet in caliper. Jaw of Leveridge Gauge rests against jaw of caliper. D. Measuring table diameter. Use 10x.

D

Fig. 7

Measuring full depth, A. With a micrometer. B. With Leveridge Gauge. Girdle diameter may also be measured with either instrument.

Fig. 7. To lessen the margin of error, it is advisable to use the same measuring device for all the measurements, whenever that is possible.

E. Measuring crown height. Diamond held in "Crown Height Attachment" of Leveridge Gauge. Use also for girdle thickness and pavilion measure-ment. Use 10x.

13

Diamond Proportion Analyzer. This "Chart" assists in the easy conversion to proportions from MM measurements.

Converting the measurements into proportions requires several exercises in simple arithmetic. Divide each of the diamond's measurements by its girdle diameter. For example:

Table diameter divided by girdle diameter equals table proportion

Crown height divided by girdle diameter equals crown proportion

Distance culet is off-center divided by girdle diameter equals percentage of off-center culet.

When the measurements are known, the proportions may be read directly on the Diamond Proportion Analyzer as shown in Fig. 8.

2.Direct reading of proportions—without the linear measurements — is provided by use of one of the adap-tations of the ideal proportion diagram as shown in Fig. 9. This diagram is incorporated into the eyepiece reticle available with the zoom-lens model of the Diamondscope.

14

A B C

Fig. 10

A. The AGS Diamondscope with stereo-zoom magnification. An auxiliary eyepiece contains the Diagram of Ideal Proportions. (See Fig. 9). B. C. and D. Each of these instruments also contains an adaptation of the Diagram of Ideal Proportions.

D

15

ni 1 1

Fig. 9

The Diagram of Ideal Proportions is used in taking direct readings of proportions. The silhouette of the diamond is projected on the diagram. (See Figs. 10 and 11.)

110 130

B

130 110

Special stoneholder for use with pro-jection devices shown in Fig. 10. Rigidly holds diamond table to culet. Stone must be held so view is parallel to girdle plane, with table, girdle and culet all in view.

16

The Mark V Gemolite, other zoom-lens microscopes, or special projection instruments may be equipped with the Diamond Proportion Screen. A telescoping model of the Proportion Screen is available for older models of the Diamondscope and other non-zoom microscopes. Figs. 10 and 11 illustrate this equipment and its applications.

Fig. 11 11

130 110

Projected silhouette must show slope of bezel facet rather than star and upper girdle facets. The girdle edges of silhouette must coincide with girdle edges of diagram. Illustration A shows 13% crown, 60% table, and 46% pavilion. B shows 18% crown, 50% table and 37% pavilion.

3.A third method of analyzing the proportions and major symmetry of a diamond is the Table Reflection Method which is described in editions of the GIA Diamond Course published subsequent to 1962. Articles on the subject have also appeared in Gems and Gemology, Vol. X, Nos. 11 and 12. This method, involving estimation of diamond proportions by eye, may be properly practiced only by those who have been thoroughly trained, and who have gained sufficient practice in the technique. Here again, the AGS member must bear in mind his responsibility for accuracy in the application of AGS Diamond Grades.

B. When making measurements and determining proportions by any of the foregoing methods, the following uniform rules must be observed.

Girdle diameter. Use the average girdle diameter to deter-mine all proportions and major symmetry percentages. If the girdle is out-of-round measure the maximum and mini-mum girdle diameter. Use the differenCe between the maxi-mum and minimum to determine the deduction for the Girdle Diameter Variation.

Table diameter. Measure table from corner to corner — not from side to side.

Table diameter variation. If table is irregular, measure and record both the maximum and minimum table diameter ( corner to corner ). Use the figure which calls for the larger deduction.

Table off-center. If the table is noticeably off-center under 10X, measure from a point directly above the center of the girdle plane to the farthest corner of the table. Use double this figure to determine the table deduction as shown in Fig. 12.

Crown height._Measure crown height from the point where the bezel facet meets the girdle. Do not include any part of the girdle thickness.

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C

Measuring an off-center table. Double the distance B-A rather than using the distance C-A

Fig. 13

Tilted table.

Table tilted with respect to girdle plane as shown in Fig. 13. Consider this cutting fault as a variation in crown height. If the table is not parallel to the plane of the girdle, measure and record the largest and the smallest crown height. Use the figure which calls for the larger deduction.

Fig. 14

When measuring girdle thickness measure at point, A, rather than at B, C, or D.

Girdle thickness. Measure girdle thickness at a point where a bezel facet and its corresponding pavilion facet meet the girdle, as shown in Fig. 14. If the thickness of these eight points varies, measure the one of average thickness.

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Girdle thickness variation. If there is a noticeable difference in the thickness of similar parts of the girdle, measure and record that difference.

Pavilion depth. Measure pavilion depth from the point where the pavilion facet meets the girdle. Do not include any-part of the girdle thickness.

Culet off-center. If the culet is not centered, measure and record its displacement from the center of the diamond.

C. Assessing the finish and symmetry details.

The surface of the diamond must be examined under 10X magnification, using the Diamondscope or equivalent magni-fier. Deficiencies in polish must be noted, as well as deficien-cies in the placement, shape, symmetry, and alignment of the facets, girdle, and culet. Also, the diamond must be examined in a direction parallel to its girdle plane while the stone is revolved on its table to culet axis for observation of faulty alignment of crown facets to corresponding pavilion facets —as well as variations of the girdle plane (wavy girdle).

III. Applying the deductions.

When the proportions, the major symmetry faults, and the deficiencies in finish and symmetry details have been recorded, find the applicable deductions in the deduction tables which follow.

The work sheet shown on page 25 provides space for record-ing all the possible cutting faults. Few diamonds, however, will require entries in all the spaces provided. Entries for Pro-portions should be made in all cases. Measurements and nota-tions for Major Symmetry and for Finish and Symmetry Details should be made only when faults in these areas are present. Typical completed work sheets are illustrated in the Appendix.

In applying the deductions and filling out the Work Sheet, the following points should be borne in mind.

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A. The average girdle diameter is recorded as 100%.

B. A deduction is applied for a girdle diameter variation, when present.

C. Only one deduction is made for the table diameter. If there is a variation in the table diameter, and, in addition the table is off-center, then the largest of the three possible deductions is applied.

D. Only one deduction is applied for the crown height, even when a maximum and a minimum are recorded to account for a tilted table.

E. Deductions for variation in girdle thickness, when present, are taken from the Girdle Thickness Table. If part of the girdle is knife-edged, apply an additional deduction.

G. Deductions for finish and symmetry details are based on judgement, not measurements. They are applied in addi-tion to those for proportion and major symmetry faults.

H. When the total of deductions for finish and symmetry details exceeds 1.5, apply the maximum deduction of 1.5 only.

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IV. DEDUCTION TABLES

See the following two pages.

21

TABLE DIAMETER

PERCENTAGE MEASUREMENT DEDUCTION

45 - 46 1.5 47 - 48 .9 49 - 50 .5 51- 52 .2 53 - 57 .0 58 .2 59 .4 60 .6 61 .8 62 1.0 63 1.2 64 1.4 65 1.6 66 1.8 67 2.0 68 2.2 69 2.4 70 2.6 71 2.8 72 3.0

IV. DEDUCTION TABLES

GIRDLE DIAMETER VARIATION


0 - 1.5 1.6 - 2.0 .2 2.1,- 2.5 .4 2.6 - 3.0 .6 3.1 - 3.5 .8 3.6 - 4.0

1.0 4.1 - 4.5

1.2 4.6 - 5.0

1.4 ,

5.1- 5.5

1.6 5.6 - 6.0

1.8 6.1 - 6.5

2.0 6.6 - 7.0

2.2

CROWN HEIGHT

PERCENTAGE DEDUCTION MEASUREMENT

18.6 - 19.0 1.0 18.1 - 18.5 .8 17.6 - 18.0 .6 17.1 - 17.5 .4 16.6 - 17.0 .2 15.1 - 16.5 .0 14.6 - 15.0 .3 14.1 - 14.5 .6 13.6 - 14.0 .9 , 13.1 - 13.5 1.2 12.6 - 13.0 1.5 12.1 - 12.5 1.8 11.6 - 12.0 2.1 11.1 - 11.5 2.4 10.6 -11.0 2.7 10.1 - 10.5 3.0 9.6 - 10.0 3.3 9.1 - 9.5 3.6

GIRDLE THICKNESS

Diamonds weighing .40 ct or less will have no deduction up to 3.0%.


1.0 - 2.5 2.6 - 3.0 .3 3.1 - 3.5 .6 3.6 - 4.0 .9 4.1 - 4.5 1.2 4.6 - 5.0 1.6 5.1 - 5.5 2.0 5.6 - 6.0 2.4 6.1 - 6.5 2.8 6.6 - 7.0 3.2 7.1 - 7.5 3.6 7.6 - 8.0 4.0 8.1 - 8.5 4.4 8.6 - 9.0 4.8 9.1 - 9.5 5.2 9.6 - 10.0 5.6

10.1 - Over 6.0 Knife-edged depending on degree .1-1.0

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CULET OFF-CENTER

PERCENTAGE MEASUREMENT

O to .9 1 to 1.9 2 to 2:9 3 to 3.9 4 to 4.9 5 to 5.9 6 to 6.9 7 to 7.9

DEDUCTION

0 0.8 1.6 2.5 3.6 4.7 5.8 7.0

PAVILION DEPTH


Over 52 4.0 51.6 - 52.0 3.8 51.1 - 51.5 3.6 50.6 - 51.0 3.4 50.1 - 50.5 3.1 49.6 - 50.0 2.8 49.1 - 49.5 2.5 48.6 - 49.0 2.2 48.1 - 48.5 2.0 47.6 - 48.0 1.8 47.1 - 47.5 1.6 46.6 - 47.0 1.4 46.1 - 46.5 1.2 45.6 - 46.0 1.0 45.1 - 45.5 .8 44.6 - 45.0 .6 44.1 - 44.5 .4 43.4 - 44.0 .2 42.9 - 43.3 0 42.4 - 42.8 .4 42.0 - 42.3 .8 41.6 - 41.9 1.2 41.1 - 41.5 1.6 40.6 - 41.0 2.0 40.1 - 40.5 2.4 39.6 - 40.0 2.9 39.1 - 39.5 3.4 38.6 - 39.0 3.9 38.1 - 38.5 4.4 37.6 - 38.0 4.9 37.1 - 37.5 5.4 36.6 - 37.0 5.9 36.1 - 36.5 6.4 35.6 - 36.0 6.9 35.1 - 35.5 7.4 34.6 - 35.0 7.9 Under 34.6 8.4

FINISH & SYMMETRY DETAILS

Facets DEDUCTION

extra .1 - 1.2 distorted .1 - 1.2

( asymmetrical or unequal) alignment ( crown to pavilion) .1 - 1.2

Girdle, rough .1- 1.2 wavy .1 - .4

Culet, large .1- 1.2 unpolished .1 - .2

Polishing marks .1 - 1.2

AGS DIAMOND CUTTING GRADE

If Deductions AGS Cutting Total Grade Is

.0 - .5 00

.6 - 1.2 1

1.3 - 2.1 2

2.2 - 3.2 3

3.3 - 4.5 4

4.6 - 6.0 5

6.1 - 7.7 6

7.8 - 9.6 7

9.7 -11.7 8

11.8 - 14.2 9

14.3 or over 10

°Provided that no single deduction is greater than .3.

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PROPORTIONS Major Symmetry

MM MEASUREMENT PROPORTIONS DEDUCTIONS

GIRDLE DIAMETER

Girdle Diameter Var.

TABLE DIAMETER

(Max./Min.)

(Off-Center)

CROWN HEIGHT

(Max./Min.)

GIRDLE THICKNESS

Girdle Thickness Var.

PAVILION DEPTH

Culet Off -Center

FULL DEPTH

100%


DEDUCTIONS

Facets, extra

distorted

( asymmetrical or unequal)

alignment ( crown to pavilion )

Girdle, rough

wavy Culet, large

unpolished

Polishing marks

Total

( Enter above total or 1.5, whichever is smaller )

TOTAL DEDUCTIONS

AGS DIAMOND CUTTING GRADE 25

(See Appendix for examples of "filled in" Work Sheets)

COLOR

I. General Provisions. Grades of COLOR are defined in terms of the degree of de-parture from a colorless body, as measured on the American Gem Society Electronic Colorimeter. The reading obtained on the Colorimeter is converted to a COLOR GRADE on a scale of 0 through 10.

Explanatory note: The first AGS Colorimeter, introduced in 1941, employed a yellow glass wedge in a comparison microscope, providing direct comparison by eye of the amount of yellowish body color in a diamond. The scale of 0 to 6.5 ( later extended to 10 ) was arbitrary; it formed a useful yardstick for measurement of color. It did not directly reflect the color grading divisions adhered to by diamond suppliers and retailers.

The AGS Electronic Colorimeter, introduced in 1955, pro-vided much more accurate and reproducible measurements of color in diamonds. It has a scale calibrated to the scale of the original glass wedge colorimeter. Here again, the scale provides a measurement, but not a direct reading of color grade.

The AGS Diamond Grading Standards for COLOR represent the best judgment of the Diamond Standards Committee, comprising diamond suppliers, retailers, and gemological re-searchers, who have examined the color grading practices of many diamond dealers, both members and non-members of the Society.

The AGS member who makes use of these Diamond Grading Standards assumes the responsibility for accuracy in ascer-taining and reporting the COLOR GRADE. Use of the work sheet shown on page 31 is recommended to reduce the pos-sibility of error and to provide a permanent record.

27

Fig. 15

The AGS Electronic Colorimeter.


A.Grading on the Colorimeter, Fig. 15

The AGS Electronic Colorimeter indicates the amount of blue light and of yellow light transmitted by the diamond. The built-in computer converts the two readings to a color scale figure. The Colorimeter grades only round diamonds of reasonably good proportions. It will not grade fluorescent stones, nor those with a brownish or greenish tingle of color.

Details of the operation, maintenance, and employment of the Colorimeter are supplied with the instrument. It is essential that the instrument be kept clean and in correct operating condition, and that it be tested at frequent inter-vals with AGS Master Diamonds of recorded color grade. The Colorimeter is leased by the Society to its firm mem-bers, and the lease provides for technical maintenance.

Using the Colorimeter, obtain and record the two readings of light transmission and the color scale reading. Convert the Colorimeter scale reading to the AGS COLOR GRADE, using the conversion table at the end of this Section.

B.Grading by Eye.

Grading by eye involves the comparison of the body color of the diamond being tested with diamonds of known color grade, using a light source and viewing technique which will assure the greatest accuracy and reproducibility.

28

Sets of AGS Master Diamonds are graded on the Electronic Colorimeter at Society Headquarters and made available to members. A Set of Master Diamonds, to assure grading to close tolerances over the range of diamond color normally encountered, should comprise at least five stones of one-third carat or larger size. A diamond, not part of a set of Master Diamonds, which has been graded on the AGS Elec-tronic Colorimeter, may be used for comparison grading by eye when its color grade is nearer the color of the stone under examination than any available Master Diamond.

Master Diamonds, having been graded on the AGS Elec-tronic Colorimeter, are in the colorless to yellowish range. When a diamond with brownish or greenish-yellow body color is encountered, it must be graded with yellowish Master Diamonds by comparing the depth of color only.

Essentials for color grading are an ultraviolet-free north daylight or its equivalent, and freedom from color reflec-tions. The diamond being graded and the Master. Diamond with which it is being compared must be viewed together over a white background in a direction perpendicular to the pavilion facets or parallel to the girdle planes. Magnifi-cation assists in the detection of fine color differences, and permits examination of similar small areas of two stones to assure comparison of body color rather than reflected color.

Fig. 16

Color grading by eye comparison with a pre-graded Master Set. The Diamondlite provides a uniform light source.

29

The Diamondlite, Fig. 16 and the GIA Color Grader, Fig. 17, provide suitable lighting, background environment and mechanical arrangements for diamond color grading by comparison with Master Diamonds.

Fig. 17

The Color Grader and light source mounted on the

Diamondscope.

Using Master Diamonds, select the two diamonds which bracket the color of the diamond being graded. Record the known Colorimeter readings of the two Master Diamonds; then record the estimated Colorimeter reading of the dia-mond being graded. Convert the estimated Colorimeter reading to the AGS COLOR GRADE, using the conversion table at the end of this section.

III. Conversion Table.

AGS Electronic Colorimeter AGS Diamond Color Scale Grade

To .75 0

.76 — 1.35 1

1.36 — 2.00 2

2.01 — 2.50 3

2.51— 3.00 4

3.01 — 3.75 5

3.76 — 4.50 6

4.51 — 5.50 7

5.51 — 7.00 8

7.01 — 8.50 9

8.51 — 10.00 10

30

AGS DIAMOND COLOR GRADE

• COLOR ANALYZED ON AGS ELECTRONIC

COLORIMETER #

Blue Filter Reading Yellow Filter Reading

Colorimeter Scale Reading

AGS Color Grade

• COLOR COMPARED WITH AGS MASTER DIAMONDS

Master Diamond # Its Colorimeter Reading

Master Diamond # Its Colorimeter Reading

Compared Diamond: Estimated Colorimeter Reading

AGS Color Grade


31

CLARITY

I. General Provisions.

Grades of Clarity are defined in terms of the degree of departure from a complete absence of inclusions and surface blemishes, when the diamond is examined by a trained and experienced person employing binocular magnification of 10X with both dark field and direct illumination. The AGS CLARITY GRADE, 0 through 10, is determined by com-parison of the diamond under examination with previously graded diamonds through the medium of the Diamond Clar-ity Comparison Photographs and Diagrams.

For many years prior to the presentation of these proposed Diamond Grading Standards, the American Gem Society has recommended a clarity grading nomenclature starting with "flawless" and followed by "very very slightly imperfect," "very slightly imperfect," "slightly imperfect," and "imper- c

fect." The four grades following "flawless" were usually divided into two grades each. The AGS CLARITY GRADES 0 through 6 are approximately equivalent to the earlier nomenclature ( 0 is flawless, 1 corresponds to VVS 1 , 2 to VVS2, 3 to VSI 1 , etc. ) The category "imperfect" is divided into AGS Clarity Grades 7, 8, 9, and 10.

Since the grade 0 is identical with the grade "flawless," AGS Ruling B-2 which defines "flawless" becomes the definition of AGS Clarity Grade 0:

"The term flawless shall be used to des' ibe a diamond which is free from'all,internal and ex 'rnal blemishes or faults of every descriptionwider illed observation in normal, natural or artificial light ith a ten-power loupe, corrected for chromatic and •herica • • erration; binoc-ular examination under • rk field illumination is pre-ferred. No other use of the term flawless as applied to diamond shall be permitted.

33

(Note: In the i erest of clarifyin trade practice, an extra facet shall b onsidered lemish only when it can be seen directly th :h e crown, or is located on the crown. A 'natural' shall considered a blemish only when it extends beyo i the -Triaximum width of the girdle, breaks the sy etry of the shape, or can be seen on, or directly through, the crown. 'Growth lines' will be classified as flaws when they exhibit color, or break the surface of the stone.)"

The distinction between acceptable and unacceptable natu-rals attel-oittr*-faeets for Clarity Cade 0 is illustrated in Part III of this section. The only acceptable internal feature is the rarely noted, but usually present, faint parallel lines related to the growth of the diamond crystal. Since all diamonds grow by accumulation, growth lines are not considered flaws, provided that there is no surface evidence of this condition, and provided also, that the growth lines do not exhibit color.

Beyond Grade 0 it is not practical to define the grades by written description of the degree to which a diamond may contain inclusions and blemishes. The diamond grader must judge the size and number of inclusions and surface marks, their nature, location, extent, _visibility, and effect on the beauty and durability of the diamond. Typical inclusions and surface blemishes encountered in diamonds are illustrated in Part IV of this section.

Experienced diamond graders have little difficulty in achiev-ing uniform results when the Diamond Clarity Comparison Photographs and Diagrams are used as a guide. Enough variety is provided in the illustrations to permit comparison with all diamonds encountered in the gem trade. Use of the work sheet, Page 74, facilitates the grading, and provides a permanent professional record.


A. Examining the Diamond.

The Diamondscope,® or an equivalent binocular magnifier capable of 10X magnification with dark field illumination, is

34

required for clarity examination of a diamond.

Fig. 18

AGS Diamondscope®

The interior of the stone must be examined thoroughly, employing 10X magnification with dark field illumination. Diamonds which appear to be flawless or nearly so must be viewed through each facet. Inclusions may be located more quickly, and they may be more readily distinguished from surface dust and reflections by employing magnification higher than 10X. When an inclusion is located in this manner, magnification must be reduced to note its appearance under 10X.

The diamond must then be examined in reflected light, which may disclose some surface blemishes unobserved in dark field illumination. Reflected light may also cause some inclusions which appear light or transparent in dark field illumination to appear black, or otherwise more significant.

All inclusions and surface blemishes should be plotted on the diagram on the clarity grading work sheet, Page 74, using appropriate symbols and, when helpful, written descriptions.

B. Applying the Clarity Grade.

When the diamond has been examined and its inclusions and blemishes have been plotted, form a general impression of

35

the stone's relative deviation from flawlessness. Next, seek a comparable degree of clarity from among the Clarity Com-parison Photographs and Diagrams. Then, assign and record the clarity grade of the most nearly comparable diamond illustrated.

As a guide, it should be noted that inclusions and blemishes in grades 1 and 2 are difficult to see or locate under 10X, a 1 being more difficult than a 2. Oracles 5 and 6 have inclu-sions that are not visible to the unaided eye when the stone is viewed face up, but which are readily seen under magni-fication of 10X. Grades 3 and 4 are in between. In grade 7 they can be seen by the unaided eye under careful inspec-tion. Grade 8 contains inclusions likely to be visible to the unaided eye, and grade 9 has inclusions so obvious and large that they affect the brilliancy as well as the beauty of the diamond. Grade 10 includes diamonds with a shat-tered appearance or with disfiguring and dangerous inclu-sions and surface blemishes.

When a small crystal is the only inclusion, it reduces the grade less if it is near the girdle than if it is in the center of the stone. An inclusion in a position that is reflected all over the diamond has more effect on grade than another of com-parable size under the table, but not in a reflecting position. Thus, a crystal of the same size in a stone could make a dia-mond perhaps a 3, 4, or 5, depending on its location within the stone. Cleavages are more important than transparent crystals, and small naturals are less important than either.

A diamond may show an inclusion which is detected face up by the unaided eye of an experienced grader, when it should be given a grade better than 7. In a small diamond, scintillation from the small facets tends to mask inclusions which would be visible through the larger facets of a large stone. Therefore, a smaller inclusion may be eye-visible in a large diamond which couldn't be seen in a smaller stone. If an inclusion is visible with difficulty near the girdle of a large diamond, it may still be grade 6 or even 5, rather than grade 7.

36

C. Uniform Symbols for Clarity Diagrams.

Symbols appearing on the following page should be used to indicate the nature and position of clarity characteristics. External characteristics are plotted with green ink, internal wit red ink,

All clarity characteristics which are visible on or through the crown must be plotted on the crown diagram, unless they reach or are on the surface of the pavilion. Inclusions and blemishes which are equally characteristic of the crown and pavilion — rough girdle, girdle naturals, through-girdle chips — should be shown on both the crown and pavilion diagrams.

All markings on the clarity diagram must be neatly executed with a fine point, carefully depicting each clarity character-istic in its correct relative position, shape, and size. To relate the crown diagram to the pavilion diagram, consider the stone to have been turned over laterally, as the outstretched right hand is turned from a palm-down to a palm-up position. Properly executed, the diagram should make the clarity grade almost self-evident.

Written comments must explain: (1) Any clarity characteris-tic for which no symbol is plotted, (2) Diagram markings which might otherwise be misinterpreted, (3) Unusual situa-tions which necessitate marking the same characteristic on both the crown and pavilion diagrams.

Extra facets and other faceting irregularities, although not clarity characteristics, may be shown on the clarity diagrams, using black ink.

Note: Diagrams on pages 44 through 77, and on the sample work sheets in the appendix, do not now appear in red and green, nor do they follow exactly the stand-ardized symbols. Appropriate changes will be made in a subsequent printing.

March, 1968 36a

CLARITY DIAGRAM SYMBOLS

External Characteristics v Cavity (actual shape)

Nick _ -- -- External grain, knot

or twinning line Scratch or wheel mark

N Natural (draw shape on facets)

N Natural (flattens girdle) E F Extra facet (actual shape)

Rough girdle

411 Girdle chip and sliver (actual shape — solid mark for chip through girdle, shaded area for sliver)

Internal Characteristics ,--' Off-grain feather,

or off-grain hairline - Grain feather,

or grain hairline O Included crystal

(actual shape) "Carbon" spot Pinpoint inclusion

Group of pinpoint inclusions Cloud (actual shape)

K or Knot x Percussion mark or bruise

wow( Bearded, or feathered girdle

_ - - - —Internal grain, knot or twinning line

March, 1968 36b

III. The photographs on the following two pages show the distinction between acceptable and unacceptable naturals and extra facets in the consideration of Clarity Grade 0.

37

Fig. 19

The natural shown in Fig. 19 is far too large to be acceptable for 0 Clarity grade. That shown in Fig. 20 is also too large, because it is wider than the maximum girdle. Fig. 20 would also rule out 0 Clar-ity, because the girdle, plus the natural at this point, is appreciably wider than the maximum girdle. On the other hand, Fig. 21 would be acceptable because it is not wider than a medium girdle and apparently does not distort the girdle outline from above. This

i■-q11/1.4.

Fig. 20

38

Fig. 21

could be checked by viewing the stone from above. Fig. 22 is a view from above of a flat on the girdle caused by a natural (between 6 and 7 o'clock). This would eliminate the stone from consideration as a flawless stone, if it qualified otherwise.

Fig. 22

39

',.

IV. The following pages show photographs of typical inclu-sions and surface marks encountered in diamonds.

40

The appearance of a carbon

spot in darkfield.

Cleavage at 3 o'clock, table

to star.

Polishing marks or running

lines, stars.

41

Bearded girdle, 7 to 9 o'clock and 10 to 11 o'clock.

Twinning lines from 6 to 8 o'clock, near girdle.

Cloud under table.

be

Included crystals.

42

V. The following pages of Diamond Clarity Comparison Pho-tographs and Diagrams illustrate the AGS Clarity grades from 1 through 10. Magnification is 10 power. The index numbers adjacent to the Photographs and Diagrams are for reference purposes. The index "2-4" means the fourth example of AGS Clarity Grade 2; "1-1" means the first example of AGS Clarity Grade 1, etc.

43

Clarity Grade Number 1

1 — 1 Pinpoint near heart.

1 — 4 Two faint bruises. Faint

bearding.

1 — 2

1 — 3 )ThIcfrP!Ei' and natural on

Scratch on table.

crown side of girdle are blemishes. Pinpoint.

44


1 —5 Pinpoint under star facet only inclusion.

1 — 7

Pinpoint centered in table.

1 — 6 One pinpoint under star facet. One scratch on lower-girdle facet.


1 — 8 Group of small pits on table

surface.

1 — 9 Two pinpoints.

1-10 Pinpoint and scratch on table.

1-11 Two pinpoints under bezel

facet.

1-12 Pinpoint, nick and natural.

46

2 — 1 Pinpoints, heart.

2 — 3 Pinpoints under table.

47


2 — 2 Very tiny cleavage near culet. Two naturals, one indented, on pavilion.

2 —7

Crystal, heart.


2 — 8 Several pinpoints, table and crown. Natural on crown side of girdle.

Trorvre.34perfarets, pavilion.

2 — 9 Crystal in star facet is seen reflected in bezel facet.

49


3-2 Faint cloud of pinpoints, table; natural, metmr4e.eet, small cleavage near

girdle.

3 — 3 Crystals and pinpoints; faint bearding.

50

3 — 1 Crystal, table; bearded girdle.

3 — 4 Crystal and nick, table; pin-

points, crown.

3 — 6 Pinpoint, table; scratch on star facet.

51

3 — 5 Very small irregular inclusion under table edge, two naturals.

3 — 7 White line, upper girdle facet; pinpoints, table.


3 — 8 One small "carbon spot," table edge; two crystals, star facet; pinpoint,

table; one natural.

3 — 9 Groups of pinpoints, table.

52

4-1 Crystal, center; small cleavage at girdle.


4-2 Two cleavages, extra facet and natural, pavilion; pinpoints,

4-3 Small crystal under table edge reflects in star and bezel facets;

scratch bezel facet; two tiny cleavages at girdle. 53


4 — 5 Crystals, table; cleavage near girdle; two naturals, one indented)-emret

facet, pavilion.

54


4 —7 Crystal, table; nick, bezel facet.

4-9 Crystals, table and near girdle; girdle bearded in part.

4 — 8 Two tiny cleavages, crown near girdle. Two small cleavages, pavilion facet.

Tiny fissure on upper-girdle facet.

55


5 — 1 Several crystals, table.

5-3 Crystals and pinpoints, table. Natural; bearded.

5 — 2 Two cleavages. Two included crystals, one dark. Several pinpoints.

ctwzf=.t crown. Natural.

56


5 — 4 Cleavage at side, plus crystals

and clouds.

fri...*, 4 lip 'kJ

5-5 Crystals under crown.

5-6 Cleavages, table and girdle;

scratch, bezel; naturals, girdle

57

5 — 7

Crystals, bezel facet; pinpoints, table.

5 — 9 Cleavage, bezel facet; crystals, table

and bezel facet. 58


5 — 8 Only fairly large irregular inclusion. Large nick on girdle. Abraded culet.

6-3 Narrow cleavage alicf uAlru

toeetr Bearded.


6-1 Four prominent cloudy areas. Three naturals.

6 — 4 Clouds of pinpoints, heart; cleavages under bezel facet.

6 — 5 One thin cleavage near girdle. One small cloud under table edge. Two

naturals.

6 — 6 Small cleavages table, bezel and girdle facets;

heavy bearding. 60


g9

•)pop sioaddy .atcp -sin aAa '4araeti u! SOBDADaID

•saBonoap alcils!^ -8A3 L — L

L i a qw n N oPe.1 0 A4!Ael0

7 —4 Thin cleavages and clouds.

7 — 6 Planes of cottony inclusions. Also faint white lines.


7-5 Girdle cleavage appears as feather from above. Natural flattens girdle.

63

7 — 9

Several cleavages, natural, plus bearded girdle.

64


7 — 8 Small but prominent cleavage parallel to and just under table.


8 — 1 Huge inclusions; burned bezels.

8 — 2 One cleavage is very prominent.

8 — 3 Large cleavage, center.

65

8 — 6 Noticeable cleavages.


8 — 4 Dangerous cleavage. Bearded.

8 — 5 Multiple cleavages.

66


8 — 8

Very wide cleavages but fairly clean center.

67

9 — 3 Inclusions rate 8, but reflec-

tions bad.


68

9 — 5 Cleavages throughout.


9 — 4 Flaws very obvious.

9 — 6 Very obvious.

69

9 — 8 Very dangerous cleavages.


9-7 Almost industrial.

9 — 9 Likely to break apart.

70


i■pp.

Or 441 vkle 40,► rp q*ak' 10_1

Reflecting cleavages cause

shattered appearance.

10-2

Thick cloud throughout reduces transparency materially.

10-3

Likely to fall apart.

71


10-4 Shattered culet and cleav-

ages throughout.

10-5 This color-filled fissure gives whole stone a shattered look.

10-6 Borderline nine, but cleavages prominent and likely

to break out. 72

10-7 Cleavages give cloudy look

throughout.

10-9 Cleavages reflect and very

dangerous.


10-8 Very obvious black inclusions plus several cleavages that reflect

completely and bad fissure.

AGS DIAMOND CLARITY GRADE

Inclusions and surface blemishes:

Compared with Clarity Comparison Photographs and Diagram #

AGS CLARITY GRADE


74

CARAT WEIGHT

Fig. 23

Diamond Scales.

The Carat, the standard unit for the designation of the weight of all diamonds, is equivalent to two hundred milligrams, or one-fifth of a gram.

Weight of the diamond being graded is determined by weigh-ing on an accurate diamond balance having a sensitivity of no less than .002 carat (1/5 point). The balance should be kept clean and in proper working order, and its accuracy should be tested at frequent intervals.

The weight of the graded diamond is stated in carats and hundredths of a carat ( points ), and is subject to a tolerance of 1/200th of a carat ( .005 carat). Stated another way, the recorded weight must be correct to the nearest point (.01 carat ).

75

APPENDIX

Grading diamonds according to the AGS Standards is much facilitated by using the Work Sheets. Their use contributes to the gemologist's speed and accuracy in this work, helps avoid costly and embarrasing omissions, and provides a pro-fessional record for reference and sales use.

Although the Work Sheet form appears extensive, notice that the grading can be completed without making entries in all the blanks. The number of entries required will be limited by the instruments employed and by the quality of the diamond being graded.

To demonstrate their use, three completed Work Sheets are shown in the following pages.

Work Sheet "A"

The proportions of the diamond in this example were deter-mined on the Diamondscope, using the auxiliary eyepiece containing the Diagram of Ideal Proportions (See Figs. 10 and 11 in the Cutting Section). The minimum number of entries appear because the proportions were read directly, and because the stone showed no faults of Major Symmetry nor of Finish and Symmetry Details. (The millimeter meas-urements of girdle diameter and full depth are not required for grading in this instance; however, these measurements, when noted, can be helpful in distinguishing rapidly between several similar diamonds.) The deductions applied here, and the final grade for Cutting, were taken from the tables on pages 22 and 23 in the Cutting Section.

The diamond was color graded on the AGS Electronic Colorimeter (see reverse side of Work Sheet). The final Colorimeter reading was converted to the AGS Color Grade by reference to the table on page 30 in the Color Section. When the stone was examined and found to be flawless the only entry in the Clarity portion of the Work Sheet was the grade 0.

The final AGS Grade, in the order of Cutting, Color, Clar-ity, and Carat Weight, "2/0/0-0.92 carat" in this example — completes this Work Sheet with a minimum number of entries.

Work Sheet "B"

The second Work Sheet shows the results of a slightly more complex grading procedure. In this example a Leveridge Gauge was used to obtain the millimeter measurements of the diamond. The measurements were then converted to proportions. Notice that the full depth is recorded to per-mit checking the arithmetic, even though no deduction may be applied for full depth. Notice also that deduc-tions are recorded for minor faults of Finish and Symmetry Details; yet, the total of these deductions is so small that the AGS Cutting Grade of the diamond is 0.

The color grade of this stone was determined by compari-son with AGS Master Diamonds. The Master diamonds are identified on the Work Sheet by number and Colorimeter reading. It is important that an estimate be made of the Colorimeter reading of the diamond being compared with the Master Diamond, and that the estimate be recorded.

Examination under the Diamondscope disclosed a pinpoint inclusion and a very small natural. These were plotted on the clarity diagram and briefly described in the space pro-vided. The entry on the next line indicates that the Clarity of this diamond was most nearly comparable with number 1-6 of the Clarity Comparison Photographs and Diagrams, resulting in the AGS Clarity Grade 1.

II

Work Sheet "C"

Further variations in diamond grading procedure are shown in this example. Here the proportions were read directly, using one of the proportion screen devices shown in Fig. 10. Again, as in Work Sheet "A," and in accordance with good diamond grading practices, the millimeter meas-urements of girdle diameter and full depth have been noted. One fault of Major Symmetry is noted — a variation in girdle diameter — and the proper deduction has been applied. Notice that the stone has a number of faults of Finish and Symmetry Details. Although the deductions for Finish and Symmetry Details add up to 2.4, only the maxi-mum allowable deduction of 1.5 is carried to the total deduction column.

A variation in color grading procedure is also indicated on this Work Sheet. Notice that a diamond other than an AGS Master Diamond has been used for comparison grad-ing by eye. The diamond is suitably identified and its Color-imeter reading is noted. This procedure is described on page 29 of the Color Section.

The clarity of this stone was compared carefully with two of the Clarity Comparison Photographs and Diagrams, #8-3 and #9-6. Both numbers have been recorded in this instance to back up the decision to assign AGS Clarity Grade 9.

The importance and value of using the Work Sheets is made apparent by an examination of the examples presented. Although at first glance the Cutting portion may appear com-plicated, notice that it does not call for any more information than is necessary for accurate diamond grading; the experi-enced, conscientious diamond grader automatically considers and evaluates each of these items. The Work Sheet serves as a checklist and as a guide to uniformly professional diamond grading.

III

A




GIRDLE DIAMETER 100% Girdle Diameter Var.

TABLE DIAMETER D

(Max./Min.)

(Off-Center) 6 CROWN HEIGHT /3, r

(Max./Min.)

GIRDLE THICKNESS

Girdle Thickness Var.

PAVILION DEPTH 0

Culet Off-Center

FULL DEPTH 3,5-7 5-8; 0


DEDUCTIONS

Facets, extra

distorted

( asymmetrical or unequal )


Girdle, rough

wavy

Culet, large

unpolished

Polishing marks

Total 0

(Enter above total or 1.5, whichever is smaller )

TOTAL DEDUCTIONS


©1966 AMERICAN GEM SOCIETY

AGS DIAMOND COLOR GRADE A


COLORIMETER # 3 Blue Filter Reading 2 Yellow Filter Reading

Colorimeter Scale Reading G.

AGS Color Grade


Master Diamond # Its Colorimeter Reading Master Diamond # Its Colorimeter Reading Compared Diamond: Estimated Colorimeter Reading

AGS Color Grade



Compared with Clarity Comparison Photographs and Diagrams #

AGS CLARITY GRADE

Weight C, fLZ-- Carat.

AGS GRADE a/()




GIRDLE DIAMETER

Girdle Diameter Var.

TABLE DIAMETER

(Max./Min.)

(Off-Center)

CROWN HEIGHT

(Max./Min.)

GIRDLE THICKNESS

Girdle Thickness Var

PAVILION DEPTH

Culet Off-Center

FULL DEPTH

gs lo 100%

14 (40 55, 0

bg

\ • --a--)s , 4

\ 0

1 1 S3 51. (0

FINISH & SYMMETRY DETAILS DEDUCTIONS

Facets, extra

distorted



Girdle, rough

wavy

Culet, large

unpolished

Polishing marks

D

Total ■ )4. ( Enter above total or 1.5, whichever is smaller )

TOTAL DEDUCTIONS



AGS DIAMOND COLOR GRADE


COLORIMETER #

Blue Filter Reading Yellow Filter Reading Colorimeter Scale Reading

AGS Color Grade


Master Diamond # Li 3-4 Its Colorimeter Reading c4 D Master Diamond # H -1-1—Its Colorimeter Reading

Compared Diamond: Estimated Colorimeter Reading .1 AGS Color Grade



VI 0 90 tki\1-e--R F-A_c_E--1—

CR1 3 Milk bC- 2__zu) C9-

Compared with Clarity Comparison Photographs and Diagrams # 1 — (O.

AGS CLARITY GRADE

Weight \ Carat.

11>R AGS GRADE Oc `J-1

B


PROPORTIONS MM

Major Symmetry MEASUREMENT PROPORTIONS DEDUCTIONS

GIRDLE DIAMETER /0, 80 l00%

Girdle Diameter Var. , S - )1, I, TABLE DIAMETER

(Max./Min.)

(Off-Center)

CROWN HEIGHT

(Max./Min.) 4 5 GIRDLE THICKNESS

Girdle Thickness Var

PAVILION DEPTH i7//' 6 Culet Off-Center

FULL DEPTH .5:9y 55 6-1

FINISH & SYMMETRY DETAILS DEDUCTIONS

Facets, extra

distorted



Girdle, rough wavy

Culet, large unpolished

Polishing marks

Total a -

719 7

( Enter above total or 1.5, whichever is smaller )

TOTAL DEDUCTIONS



AGS DIAMOND COLOR GRADE C


COLORIMETER #

Blue Filter Reading Yellow Filter Reading

Colorimeter Scale Reading

AGS Color Grade

• COLOR COMPARED WITH AGS MASTER DIAMONDS (spec ,o_P_ 5l'oac )

Master Diamond #._L9_4/ Its Colorimeter Reading Q_ , 0 Master Diamond # Its Colorimeter Reading

Compared Diamond: Estimated Colorimeter Reading_ A, eo AGS Color Grade 'V


Inclusions and surface blemishes: 4, 6 b c 6 I IA4;

&IAA, cem- 'e a 6 , s Aa e ect..tielz

v SA -ter k 04 c 4_,I,e2j .e_

017.\, knA_A-Lei

Compared with Clarity Comparison Photographs and Diagrams # 3

AGS CLARITY GRADE

Weigh

Carat.

7.? I) 831 AGS GRADE 7/ 1-71. Y, 2-2 6 7`

Published by the American Gem Society

For Use By Its Membership

Serving the Fine Jeweler Since 1934

(D1966 AMERICAN GEM SOCIETY 3142 WILSHIRE BLVD.

LOS ANGELES, CALIFORNIA 90005

PRINTED IN U.S.A.

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