Resource Evaulation.pdfita llasbout ngetjwejkifcnjeejbceevhy

Resource evaluation

1. SibaPrasad Mohanty
Assistant Professor
Government College, Sundaragrh
Need and methods of resource evaluation
and reserve calculation of economic
mineral deposits

2. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh
Economic mineral deposits
Resource Reserve
A resource is that amount of a geologic
commodity that exists in both
discovered and undiscovered deposits.
Reserves are that subgroup of a
resource that have been discovered,
have a known size, and can be extracted
at a profit
For example, of the world's estimated oil resource of three
trillion barrels, the world's reserves are estimated at about a
third of that amount.

3. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh
What is the need for Estimation of Resources?
❖It has now developed thousands of uses for our natural resources, uses that support our modern‐day standard of
livingand for a greedy society.
❖Our demand for these materials far exceeds the amounts recycled.
❖Thus, we have a constant need to discover new deposits, which are becoming harder to find as the “easy” ones are
discovered at the surface and mined out.
❖ Geologists and scientists are beginning to look for deposits deeper below the surface, a more challenging and
expensive endeavor.

4. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh
Methods of resource evaluation
•Resource evaluation is carried out to in order to quantify the grade and tonnage of a
mineral occurrence.
•Economic Analysis:- Qualitative and Quantitative
•The aim here is to achieve by drilling to sample the prospective horizon, or strata where
the minerals of interest are deposited.
•Resource evaluation also involves
Resource estimation which may require
pattern drilling on a set grid, and in
the case of sulfide minerals, will usually
call for some geophysical techniques
like down-hole probing of drillholes,
to delineate ore body continuity within
the ground.

5. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh
•Ore-reserve estimates include the determination of (1) tonnages of ore and (2) average
grade or value per ton.
•The goal of this process:-
✓Controlling development
✓Exploration and allocation of funds
✓Deferred (prepaid), depletion(periodical), and depreciation(reduction in value) charges per
ton.
✓Capital expenditures.
Assay Maps and Sections
•It is prepared based on the type, length of the ore body and the assay value.
What is Assay value:-
•The quantity of an ore's valuable constituents, determined by multiplying its assay grade or
percentage of valuable constituents by its dimensions.
•It is a process of analyzing a substance to determine its composition or quality.
•The term is often used in the mining industry to refer to tests of ore or minerals.
What is an assay used for?
•An assay test determines the impurities present before sending a substance to a sorting
facility.
•When assay results indicate the potential value of a mineral or ore extraction site, results
may trigger a stock increase and value reassessment for the company. Conversely, poor
mineral assay results can trigger a decline in stock prices.
•An assay is a process of analysing a substance to determine its composition or quality.

6. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh
Volume and Tonnage Estimates
•The plans are drawn to scale, and areas may be scaled or measured with a planimeter.
•Areas are commonly figured in square feet and ore volumes in cubic feet.
•Volumes in cubic feet are converted into tons by multiplying the specific gravity (Relative Density) of ore minerals.
Ore Volume Calculation
•For flat-lying, bedded deposits of uniform thickness, volume computations involve merely scaling or
measuring with a planimeter the areas of the different blocks of ore bounded by mine workings and the
margins of the ore bodies and multiplying the area of each block by the average thickness of the ore in
that block. Summation of the volumes of all blocks gives the total volume of the ore.
•For broad, basin-shaped deposits, plan maps, vertical or horizontal cross sections or both may be used.
•Divide the area into a series of triangles, squares, or irregular
polygons, each of which represents the horizontal cross section
of an imaginary vertical prism of ore extending from the top to
the bottom of the deposit.
•The volume of the prism is the area of the cross section
multiplied by the depth, if the top and bottom of the prism are
plane parallel surfaces.
•The sum of the volumes of all the prisms is then the total
volume of ore in the deposit.

7. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh

8. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh
Specific
gravity

9. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh

10. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh

11. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh
grade

12. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh

13. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh

14. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh

15. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh
Ore Grade Estimation
•The accuracy of ore-grade estimates will depend on the accuracy of the samples, accuracy in
assaying, the method of combining and weighting the different samples, and the estimator’s
judgment.
•It has been shown that individual samples may be relatively inaccurate, but the weighted
average of a large number may closely approximate the actual grade of the ore.
Estimates based on Drill-Hole Data
•In such instances it becomes necessary to average the assays of core and of sludge and in
doing so to assign proper weight to the value of each.
Example:-
•Assume a 5-foot section of EX diameter hole, 48 inches of core, a core assay of 3.0 percent
copper, and a sludge assay of 3.6 percent copper. The core assay would receive a weight of
28.4 and that of the .sludge 71.6. The calculation then becomes:
Average assay = 1/100 (28.4 x 3.00 + 71.6 x 3.6) = 3.43 percent copper
•This is only applicable, when the core diameter is eqal and uniform core size.

16. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh

17. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh

18. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh
X0
X2 (1.1%)
X3 (3.3%)
X1 (2.2%)
2m
5m
1m

19. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh

20. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh
Polygonal Method
•The area of influence is determined by constructing
polygonal blocks around each hole that extend half the
distance between two holes.
•The average grade and thickness of the hole inside the
polygon is assigned to the entire polygon in order to
provide a volume for the reserve estimate.
•The volume is computed by multiplying the area of
polygons with thickness.
•Volume is multiplied with specific gravity to get tonnage.
Summation of all polygon will get tonnage and metal
content of total deposit.
• The polygonal method is used for tabular and large
lenses ore bodies.

21. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh
Triangular Method
•In this method holes are connected to adjacent holes.
•This divides the ore body into a series of triangles (T1,
T2, – – – – – -, Tn).
•Each triangle rests on the plane of the map and
represents a base area of an imaginary prism with edges
t1, t2, t3equal to vertical thicknesses of intercepted
mineralisation.
•In this method, the triangle area between three adjacent
holes, average grade and thickness of these holes are
used to compute tonnage.
•Following steps are involved in triangular method-
•Area of triangle is calculated using geometrical formula. Area (A) is
multiplied by average thickness intercepted in holes at three edges of that
triangle to get volume (V).
•Tonnage is computed by multiplying volume (V) with average specific
gravity of host rock. This will give tonnage of one triangle.
•Metal content is estimated by multiplying tonnage (step 2) and average
grade.
•Step 1 & 2 are repeated for all triangles with positive intercepts at their
edges.
•The total tonnage and metal content of deposit are arrived by summation
of values calculated for each triangle.

22. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh
•The triangular method is best suitable for flat or gentle dipping ore bodies having good continuity and correlation.
•Different formulas involved in calculation are –
•Where s is a semi-perimeter of the triangle.
•Datasheet of the triangular method will look like below-
20
15
35
125
0.4
2
2.5
3.1
29
60
21
80
SP. Gr.- 2.9

23. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh
Cross Section Method
•The ore body is divided into different segments with the
help of transverse section lines.
Computation steps
•The total ore body is divided into sub-blocks along section line and a
length equal to half of the distance between the adjoining sections.
•For computation of reserve, volume of each sub-block is required.
The volume is calculated by multiplication of sectional area with half
the distance of adjoining section on each side (i.e. area of
influence).
•The sectional area of ore body is calculated by geometric formula.
AutoCAD software can be used to measure area of irregular ore
body.
•Tonnage for each sub-block is calculated by multiplication of volume
and specific gravity.
•Metal content of each sub-block is calculated by multiplying tonnage
and average grade of that sub-block.
•Total tonnage of ore body is summation of sub-block tonnages.
Similarly, total metal content is summation of sub-block metal
contents.
•Average grade of ore body is total metal content divided by total
tonnage in percentage term.

24. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh

25. Siba Prasad Mohanty
Assistant Professor
Government College, Sundaragrh
Inverse Distance Weighted Method
•Inverse distance method belongs to the class of
moving average methods. It based on repetitive
calculations and therefore require the use of
computers.
•Inverse distance method can be applied to
deposits with simple to moderate geometry and
with low to high variability of grade.
•Unlike polygon method, inverse distance method
utilizes the values of all surrounding holes by
given certain weights.
•The weights are determined by the distance
between the holes and the center of the block
considered for computation.
W
x =
∈????????????/????????????
∈??????/????????????
Wi= Grade of the known location
Di= Distance between known
and unknown location.
https://www.youtube.com/watch?v=h82CEdN1yL8