Pemodelan & Analisa CadanganHendra Harisman, ST., M.Eng.Sc.

24 MARET 2015

RESOURCE ESTIMATION METHODOLOGYHendra Harisman, ST., M.Eng.Sc.

MINING SYSTEM

Sample Weighting• It is often necessary to compute a value for a composite

sample, developing a weighted average for unequal sample widths or lengths.

a series of samples collected from a vein exposure in a raise in a hypothetical lead-silver mine.

Sample Weighting• samples are collected at regular intervals with the interval

dependent on the nature of the mineralization• Erratic mineralization, such as is common in epithermal gold-

silver deposits, requires sampling at much closer spacing than more regular deposits

Sample Weighting

Sample Length(ft)

Width(ft)

S1 6.0 3.0

S2 7.5 2.5

S3 10.0 3.0

S4 12.5 2.3

S5 10.0 2.0

S6 5.0 2.6

Total 51.0 15.4

Sample Weighting

Sample Length(ft)

Width(ft)

Area(ft2)

S1 6.0 3.0 18.00

S2 7.5 2.5 18.75

S3 10.0 3.0 30.00

S4 12.5 2.3 28.75

S5 10.0 2.0 20.00

S6 5.0 2.6 13.00

Total 51.0 15.4 128.50

Sample Weighting

Sample Length(ft)

Width(ft)

Area(ft2)

Pb(%)

S1 6.0 3.0 18.00 6.4

S2 7.5 2.5 18.75 7.6

S3 10.0 3.0 30.00 5.6

S4 12.5 2.3 28.75 8.8

S5 10.0 2.0 20.00 8.2

S6 5.0 2.6 13.00 6.7

Total 51.0 15.4 128.50

Sample Weighting

Sample Length(ft)

Width(ft)

Area(ft2)

Pb(%)

AgOz/ton

S1 6.0 3.0 18.00 6.4 11.3S2 7.5 2.5 18.75 7.6 14.7S3 10.0 3.0 30.00 5.6 8.6S4 12.5 2.3 28.75 8.8 12.9S5 10.0 2.0 20.00 8.2 13.7S6 5.0 2.6 13.00 6.7 10.8

Total 51.0 15.4 128.50

Sample WeightingSample Length

(ft)Width

(ft)Area(ft2)

Pb(%)

AgOz/ton

S1 6.0 3.0 18.00 6.4 11.3S2 7.5 2.5 18.75 7.6 14.7S3 10.0 3.0 30.00 5.6 8.6S4 12.5 2.3 28.75 8.8 12.9S5 10.0 2.0 20.00 8.2 13.7S6 5.0 2.6 13.00 6.7 10.8

Total 51.0 15.4 128.50

Average Grade Pb = 7.2%

Average Grade Ag = 11.9 Oz Ag/ton

Average Thickness = 2.52 ft

Mining Dilutionprevious example:• the correct method of dealing with irregularly spaced samples

when evaluating material of uniform density

• Wall rock, or other sources of dilution will frequently have a lower density than metallic sulfides, such as would occur in a polymetallic vein, and calculations of the effect of dilution must account for this.

Mining DilutionUsing the previous example:• assume that the minimum mining width is 3 ft• Assume that the tonnage factor for the vein material is 9

ft3/ton• Assume that the tonnage factor for the wall rock is 12 ft3/ton

Mining DilutionUsing the previous example:• assume that the minimum mining width is 3 ft• Assume that the tonnage factor for the vein material is 9 ft3/ton• Assume that the tonnage factor for the wall rock is 12 ft3/ton

Sample Length(ft)

Width of Ore(ft)

Width of Waste(ft)

S1 6.0 3.0 0.0

S2 7.5 2.5 0.5

S3 10.0 3.0 0.0

S4 12.5 2.3 0.7

S5 10.0 2.0 1.0

S6 5.0 2.6 0.4

Mining DilutionUsing the previous example:• assume that the minimum mining width is 3 ft• Assume that the tonnage factor for the vein material is 9 ft3/ton• Assume that the tonnage factor for the wall rock is 12 ft3/ton

Sample Length(ft)

Wo(ft)

Ww(ft)

Ao(ft2)

Aw(ft2)

S1 6.0 3.0 0.0 18.00 0.00S2 7.5 2.5 0.5 18.75 3.75S3 10.0 3.0 0.0 30.00 0.00S4 12.5 2.3 0.7 28.75 8.75S5 10.0 2.0 1.0 20.00 10.00S6 5.0 2.6 0.4 13.00 2.00

Total 128.50 24.50

Mining DilutionUsing the previous example:• assume that the minimum mining width is 3 ft• Assume that the tonnage factor for the vein material is 9 ft3/ton• Assume that the tonnage factor for the wall rock is 12 ft3/ton

• Weight of vein material per vertical foot = ?• Weight of wall rock per vertical foot = ?• Weight of combined material = ?• Lead grade = ?• Silver grade = ?

Calculation by Mining Blockmethod of estimating tonnage and grade of an ore block:

Mining Dilution

From figure:• represents a block of ore between two levels 100 ft apart. • The vein in this area is assumed to exceed the minimum mining width of 3 ft. • The method of calculation is simply an extension of the method of sample

weighting illustrated earlier.

Mining Dilution

From figure:• represents a block of ore between two levels 100 ft apart. • coordinates 00E and 250E. • The tonnage factor is 9 cubic ft per ton.

Mining Dilution

Length (ft) Width (ft) Thickness (ft)

Tonnage Factor

50 50 3.5 950 50 4.0 950 50 5.0 950 50 4.0 950 50 3.0 950 50 3.0 950 50 3.0 950 50 5.0 950 50 6.0 950 50 4.0 9

Mining Dilution

Length (ft) Width (ft) Thickness (ft) Tonnage Factor Tons Ag Oz/ton Tons * Grade

50 50 3.5 9 972 5.0 4,861 50 50 4.0 9 1,111 7.0 7,777 50 50 5.0 9 1,388 10.0 13,889 50 50 4.0 9 1,111 8.0 8,888 50 50 3.0 9 833 7.0 5,833 50 50 3.0 9 833 5.0 4,166 50 50 3.0 9 833 6.0 5,000 50 50 5.0 9 1,388 8.0 11,111 50 50 6.0 9 1,666 9.0 15,000 50 50 4.0 9 1,111 8.5 9,444

11,246 85,972

Mining Dilution• Average Grade = ??