ISSN:
1573-8868
Keywords:
sampling
;
simulation
;
statistics
;
assay weighting
;
economic geology
;
geochemistry
;
mining
;
ore-reserve calculations
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Mathematics
Notes:
Abstract Weighting of vein assays is desirable where assays represent variable vein widths and variable distances along the vein. The method of weighting used is important in ore-reserve calculations and other investigations. Two possible methods are considered here. The first method, commonly applied in mining, assumes in effect linear variation of assay-width products between assay points. The second method, developed in this paper, assumes linear variation of assays and widths separately. The weighted average assay in an interval dby the second method (aw1, 2)is given by the expression $$a_{w1,2} = V/[(w_1 + w_2 )/2]$$ where $$\begin{gathered} v = (1/3)(\Delta a)(\Delta w)d + (1/2)(\Delta a)w_1 d + (1/2)(\Delta w)a_1 d + a_1 w_1 d \hfill \\ \Delta a = a_2 - a_1 {\text{,}}\Delta w = w_2 - w_1 \hfill \\ \end{gathered} $$ a1, w1 are assay and width at point 1, a2, w2 are assay and width at point 2,and dis the distance between points 1and 2.Statistical testing of the two methods, using 8,913 pairs of copper assay-width data from the Belmont mine area at Butte, suggests the following: within major veins or within veins which show near-linear width variations, the second method may be used with the expectation that the average grade calculated will more closely represent the actual average grade than if the first method were used.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02082888
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