274 TH E AM ERICAN MINERALOGIST

dance, as well as of silica and the principal metallic oxides, with their respective

contributions to the rock-forrning minerals. By means of a table the speaker showed

why these rock-forming minerals are common, on the basis of the proportions of

the eleven commonest elements in the earth's crust.

In closing, the speaker discussed the formation of several types of minerals

from magmas containing a maximum and a minimum proportion of silica.

A rising vote of thanks was extended to the speaker.

Jmans F. MontoN, SecrelarY

Minutes of the May Meeting-

A regular monthly meeting of the New York Mineralogical Cub was held at the

American Museum of Natural History on the evening of May 21, 1930, with Presi-

dent Frederick I. Allen in the chair. There were 36 members present.

Mr. E. B. Chapin of Tenafly, N. J., Mr. George B. Wilmott of Brooklyn, N. Y',

and Mr. Wm. H. McClelland of New York, N. Y., were elected to membership.

Sir William Henry Bragg was unanimously elected an honorary member of the

Club. It was voted to present him with a diplcima on behalf of the Club.

Professor Paul F. Kerr of Columbia University was the speaker of the evening,

his subject being ",4 Mod.ern Mineralogical Stul'y of Clay'" He dwelt on the appli

cation of X-rays and microscopic methods to the study of clay, and illustrated the

methods in a practical way by descriptions of several types of clay, emphasizing

the following points:The clay minerals have long provided one of the most difficult fields of mineral-

ogical endeavor, due largely to the extremely finely divided nature of the material.

In recent years, however, methods have been developed, which give promise of

solving problems that have long existed concerning the nature of the clay minerals.

The two most prornising lines of study are a direct outgrowth of X-tay methods and

petrographic research. These developments are now proving most valuable auxili-

aries to the time-honored method of chemical analysis.

One of the most interesting results of this study is a reduction in the large num-

ber of mineral species generally attributed to the clay group'

An interesting discussion followed the address, and a rising vote of thanks

expressed the appreciation of the members.

Jluns F. Montom, SecretarY

NEW MINERAL NAMES

Arandisite

F. C. Penrnrocn: A new tin mineral from South-west Africa. Trans. Geol..

Soc. , S. Afr ica,32, 17l-176, 1930.

Naur: From the locality, Arandis.

Cnnurclr PnopBnrrrs: A silicate of tin. Analysis (by H. G. Weall): Moisture

5.0, Ign. Ioss3.5,SiOz76.2,Al2Ot2.7,FezOr1.3,Cu0.9,SnO270.9; tota l 100'5 ' Decom-

posedby sulphuric acid. Does not reduce with zinc and HCI. B. B. infusible but

turns brown or black. In closed tube yields water which is faintly alkaline to litmus.

The mineral does not darken. With fluxes yields dispersed beads of tin. With

cobalt nitrate gives a blue crust.

TOURNAL MINERALOGICAL SOCIETTI OF AMERICA )ts

Puvsrcar, mro Oprrc.lr- PnopBnrrns: Color, varies from pale green throughbright green to deep grayish green, with bright apple green as the predominantshade. Luster, waxy to resinous. Streak, nearly white with tinge of yellowishgreen. Fracture, subconchoidal to uneven. H:5. Sp. Gt.4.12. Mainly isotropic.Made up of two components, a pale green to colorless one (n:1.7O6) and green togreen yellow fibers of varying size (n:1.82). Apparently a colloid showing incipientcrystallization.

Occunm.rce: Found in a tin mine 23 miles north of Arandis, SouthwestAfrica, with cassiterite, quartz and iron and copper sulfides in limestone. (T. W.Geversl a hydrothermal Deposit of Cassiterite near Arandis, Southwest Africa.Trans. Geol. Soc. S. Africa,32, 65-170, 1930).

W. F. Fosneo

Maufite

F, E. Knnp: Notes on Nickel Occurrences in the Great Dyke of SouthernRhodesia. Trans. Geol. Soc., S. Africa,3z, 103, 1930.

Nam; 1tt honor of H. B. Maufe, Director of the Southern Rhodesia GeologicalSurvey.

Crourcar Pnoprnrrrs: A silicate of nickel, aluminum and other bases;(Mg,Ni'Fe)O.2Al:Oa. 3 SiOr. 4HrO. Analysis (by E. Golding): SiOz 33.26,AlzOa36.81, FezOr 0.79, FeO 0.68 CaO tr., NiO 4.28,HrO+ 13.67, HrO- 5.71. Total99.98. No Co2, TiOr, SO3, Cl, F,Zr2Os, CreO3, BaO, MnO, or CuO.

Puvsrcar. lr.ro Oprrcar, Pnoprnrlns: Color emerald green, slightly dichroic.Made up of fibrous sheaves at acute angles with one another. Optical elongationnegative. H-3. Sp. Gr.2.27.

Occrrnnntcn: Found as a quarter-inch seam in dark red speckled serpentinerock adjacent to a small dolerite dyke, one and one half miles northeast from theUmvukwe Geodetic Station, Umvukwe Mts.. Southern Rhodesia.

w. F. F.

ZamboniniteF, Srrr-r,e Stlnnlssl: Zamboninite-una nuova specie minerale. Boll. Soc.

Geol,. I to.l., 48, pp. 259-263, 1930.Crmurcar Pnoprnrres: Calcium magnesium fluoride; formula: CaFr.2MgFr.

Analysis: Mg 24.26, Ca 17.94, Mn not determined, Al 0.41, Fe trace, Na 0.31,K 0.05, F 55.57, HzO 1.63; Sum 100.17. No Si, .CI, S. Easily fusible beforethe blowpipe with intumescence, forming finally an infusible mass. Partly solublein conc. HCI and HNO3; soluble in H2SOa, with evolution of HF.

Cnvsrar,locnepnrc Pnopanrrns: Not determined, probably orthorhombic.Prrvsrcnr, exo Oprrcnr, Pnopnnrrrs: Finely radiating fibrous structure, cblor

white. Sp. Gr. 2.98-3.@. Birefringence weak, biaxial positive, parallel extinction.z maximum: 1.411, minimum: 1.405.

OccunnrNcn : Forms small masses on crevices of lava of 1669, at Monti Rossi,Etna, from fumarole deposits.

H. S. Wlsrrrxcrot

276 THE AMERICAN MI NERA LOGIST

ADDITIONAL DATA

Krarnerite

W. T. Scnar,rnn: Borate minerals from the Kramer District Mohave Desert,California. U. S. Geol. Suru. ProJ. P aper, t58, 139-146, 1930.

N.lur: From the locality: Kramer, California.Cnrurclr, Pnopnnrrns: A hydrous borate of soda and lime. Nar0.2CaO.

5BrOB 10HrO. Analysis: NazO 8.34, CaO 15.11,820849.30, Il2O25.40, SiO, 0'57'Alros 0.42, Insol. 1.55. Sum 100.93 (average of 3 analyses). Soluble in hydro-chloric acid.

Heated in closed tube, decrepitates, gives ofi water, turns opaque white, swellsslightly and fuses imperfectly to clinkerlike masses. Before the blowpipe fusesreadily to a clear bubbly glass, giving a yellow flame.

Cnvsr,lrrocnlpRrcnr PnopBnrrrs : Monoclinic, prismatic. aib i c : !.IOSI i I i0.5237. P:72'76t po':9.4976, qs':c:0.5237, e' :0.3197. Forms o(100), b(010)'m(rr}), e(011), r(101), d.(r}r), p(rrl), o(rrr).

Pnvsrcnr aNo Oprrclr- Pnoprntrns: Colorless, transparent. Cleavage rz(ll0)perfect. Luster vitreous and shining. IJd.4+. Sp. Gr. 2.141.

Biaxial, positive. 2V:73", 2E:126'. Dispersion p)r. Elongation positive.a:1.515, A:7.525,t:1.5M. Plane of the optic axes is paral lel to b(010). [ :6'Z \c:12".

OccunnnNcn: Found as radiating prismatic needles in clay, massive boraxor kernite at the Kramer District. Kern Co.. Calif,

DrscussroN: [This mineral has been described under the name probertite byA. S. Eakle, Am. Mi.neralogisl, 14;427,1929. The analysis given there difiersgreatly from those given by Schaller. W. F. F.l

w. F. F.

Kernite

War.onuen T. Scnar-rnn: Borate Minerals from the Kramer District, MohaveDesert, California. fl. S. Geol. Sun. ProJ. Paper,158, pp. 137-170, 1930'

Original Description: This Journal, 12, p.24-25, 1927.Cnvsulrocnlprrrcar- Pnoprnrrus: Monoclinic, habit domatic. aibic:1.5230:

l : t .6989. 0:71o08', ps':1.1788, qs':1.6989, e' :0.3417. 32 forms of whichc, (001), a, (100), e(011) and D(101) are the common ones. Cleavages c and operfect, D distinct; perhaps e and 6 also.

Oprrcrr. Pnopnnrrns: Biaxial negative. 2V=80o, 2E:142'. Dispersiondist inct ptv. a:1.454, P:1.472, z:1.488. Plane of the optic axds is normal tob(010) ; X and I lying in the plane of symmetry, and Z : b. X AC : 7 0+".

w. F. F.

234 GEORGE TUNELL

Photo b9 Walter Stoneman of f . Russell and Sons, London

WILLIAIVI LAWRENCE BRAGG

RncrpmNr or rrrE RoEBLTNG MEDAT, ol rHEMnvBnalootcel SocETy ol AilrFRrcA

PRESENTATION OF THE ROEBLING MEDAL OF THEMINERALOGICAL SOCIETY OF AMERICA TO

WILLIAM LAWRENCE BRAGG

INTRODUCTION

GroncB TuNnr,i,

Uni,versi'ty of Cali'fornia, Los Angeles, CaliJornia.

In 1936 the Council of the Mineralogical Society of America directed

that a medal be designed in honor of Colonel Washington Augustus

Roebling. Colonel Roebling's interest in mineralogy began while he was

a student at Rensselaer Polytechnic Institute. He became closely asso-

ciated with the Mineralogical Society of America immediately after its

organization, and in 1924 served as its Vice-President. His support of

the Society and its Journal and his bequest of his comprehensive collec-

tion to the United States National Museum will long be remembered by

mineralogists. The award of the Roebling Medal was to be made for

notable contributions to mineralogy in America and abroad.The idea that crystals are built up of units put together in'a regular

way has been in the minds of mineralogists since the time of Hooke and

Guglielmini. The mathematical theory of regular three dimensionalstructures built up of identical units was carried to completion in the

latter part of the nineteenth century largely independently by Fedorov,

Schoenflies and Barlow. Ilowever, no physical method then existed by

which the arrangement of the constituent particles in any crystal could

be determined. In 1912 the diffraction of r-rays by crystals was discov-

ered by von Laue with the experimental aid of two assistants, Friedrichand Knipping. At that time Sir William Bragg had been studying the

ionization efiects of r-rays a.nd had concluded that *-rays are corpuscularin nature. His son, W. L. Bragg, now Sir Lawrence Bragg, attempted tofind an explanation for von Laue's results in terms of corpuscular lt-taYStbut soon concluded that the wave explanation of von Laue was correct.However, Sir Lawrence also realized that some features of von Lauets ex-planation could not be correct. The shapes of the spots and their behaviorwhen the crystal was tilted suggested to Sir Lawrence that c-rays, notjust of certain specific wave-lengths as von Laue had supposed, but of a

range of wave lengths-analogous to white light in the visible region-

were reflected from crystal planes. From this work the fundamental equa-tion of r-ray diffraction has become known as Bragg's law. Soon after-ward he made r-ray photographs of potassium chloride and sodiumchloride and deduced their complete atomic arrangements; these were thefirst crystal structures analyzed, and, as is well known, this achievement

235

236 GEORGE TUNELL

has lBd to the development of a new branch of science which deals withthe atomic arrangements in matter.

The invention of the ionization spectrometer by W. H. Bragg markedanother important advance, and by its application the structure of thediamond was elucidated by W. H. and W. L. Bragg. With the aid of thisnew instrument W. L. Bragg in 1913 solved the structures of sphaleritepyrite, fluorite and calcite.

After these simple structures had been analyzed it became possible toattack successfully those of lower symmetry. Thus, in t924, W. L. Braggdeduced the arrangement in the orthorhombic mineral aragonite. Thesilicate minerals make up most of the earth's crust; they often occur ingood sized crystals suitable for investigation by the ionization spectro-meter and partly for this reason they became a special object of studyby Sir Lawrence and his collaborators. Their analyses of diopside, olivine,chrysotile, beryl, phenacite, willemite and others of this class revealedthe basic features of the constitution of the silicates and revolutionizedour conceptions of the chemical bonds that cement their crystal edificestogether. In the investigations of these complicated structures use wasmade of the representation of the distribution of electron density in thecrystals by Fourier series; this numerical and graphical method, firstsuggested by W. H. Bragg, has been perfected by W. L. Bragg and sub-sequent workers, and today is widely applied in investigations of atomicarrangements.

One of the chief reasons why we are much concerned with the finestructure of matter is that it gives us the key to so many physical andchemical properties. The nature of the dependence of the optical proper-ties on the atomic arrangements in crystals was shown by W.L. Bragg'scalculations of the refractive indices of aragonite and calcite from theirstructures rn 1924. The properties of some metallic alloys, as well as ofsome sulfide and silicate minerals, depend not only on their structures,but also on the degree of ordering into superstructures. Much insighthas been gained into the nature of order-disorder transformations bythe work of Sir Lawrence and his school. The importance of these pheno-mena in rock minerals was emphasized by Past President M. J. Buergerin his address before the Society a year ago.

In recognition of these and other contributions the Council of theMineralogical Society of America has resolved that the WashingtonAugustus Roebling Gold Medal be awarded to Sir Lawrence Bragg.

Professor Bragg was born in Adelaide, S. Australia. He attended St.Peters College in Adelaide and Adelaide University. Subsequently hestudied in Trinity College, Cambridge, where in l9l4 he became Fellowand Lecturer in Natural Sciences. In the same vear he received the Bar-

PRESENTATION OF ROEBLING MEDAL

nard Medal. In 1915 he was awarded the Nobel Prize for Physics jointlywith his father on their investigations of *-rays and crystal structures.In 1931 he received the Hughes Medal of the Royal Society and in 1946the Royal Medal of the Royal Society. From 1919 to 1937 he was Lang-worthy Professor of Physics in Victoria University of Manchester; in1937 and 1938 he served as Director of the National Physical Laboratory;since 1938 he has been Cavendish Professor of Experimental Physics inCambridge. He is a fellow of the Royal Society, Honorary Member ofthe fnstitute of Metals, Corresponding Member of the Academy ofSciences of Paris, Honorary Member of the Swedish Academy of Sci-ences, Member of the American Philosophical Society, Honorary Mem-ber of the New York Mineralogical Club, Member of the Chinese Physi-cal Society, Foreign Associate of the National Academy of Sciences ofWashington, Associate of the Royal Academy of Sciences of Belgium,Honorary Fellow of the Royal Society of Edinburgh, Honorary Memberof the Royal Irish Academy, President of the fnternational Union ofCrystallography, and President of the British Association for the Ad-vancement of Science. He is an Officer of the British Empire. During thefirst World War he served as Technical Adviser on Sound Ranging tothe Map Section of the General Headquarters in France, and wasawarded the Military Cross. During the second World War he acted asCoordinator of British, Canadian and American Military Research.

Most of the results of the researches of Sir Lawrence have appeared asscientific papers of which there has been a long series. He has also writtena number of books,of which"X-Raysand Crystal Structure"and,'AtomicStructure of Minerals" have been of particular value to mineralogists.Students, not only British but also of other nationalities, have gone tohis laboratory to learn the methods of. x-ray analysis, and from him theyhave received illuminating instruction and kind counsel. Through them,as well as directly, the stimulating influence of Sir Lawrence is felt inAmerica and other countries.

Mr. President, it is my valued privilege to introduce Professor SirLawrence Bragg.

PRESENTATION

President M. A. Peacock handed the medal to Sir Lawrence Braggwith the words:

Wrr,rau LewnnNcn Bnacc, in recognition of the fundamental andilluminating work you have done on the ultimate structure of crystalsand the impetus and direction that this work has given to the study ofminerals, f have the honour to present you with the Roebling Medal ofthe Mineralogical Society of America.

237