Principles & Assumptions in Mineral Expl.pdf

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1. Principles Assumptions and Parameters
for Resource Estimation, concept of Lode
and Mineralized zone with calculation of
lode and methodology of Resource
calculation for base metal.
Sanjoy Debnath
Senior Geologist
Field Training Centre, Zawar

2. What is a Resource and a Reserve ?
Mineral Resource: A quantifiable concentration of naturally
occurring solid, liquid or gaseous material on earth in such a
form that commercial extraction of a usable commodity is
possible within a foreseeable future.

Mineral Reserve: Part of ‘Identified Resource’ with calculable
tonnage of ore (or metal) within given boundaries and getting
divided into developed, probable and possible categories
depending on the degree of assurance of their existence.

3. Before knowing about the parameters of resource estimation in mineral
exploration along with principles and assumptions, a brief account of existing
UNFC is essential to follow the procedures.
The united nations framework classification of ore deposits or ore
resources is defined by three axis; E,F,G,

E- The degree of Economic Viability

F- Feasibility The Stages of Mineability Assessment

G-Geological axis- The stages of Geological Assessment.

5. TOTAL CODES: 36 3x3x4=36

10 CODES ARE APPLICABLE IN PRACTICE

PREFIX TO CODES : STD ( STANDARD )
EX: STD 332

7. Resources classes according to UNFC classification:
Reconnaissance Mineral Resource (334)
Inferred Mineral Resource (333)
Indicated Mineral Resource (332)
Measured Mineral Resource (331)
Prefeasibility Mineral Resource (221 & 222)
Feasibility Mineral Resource (211)
Reserve classes according to UNFC classification:
Proved Mineral Reserve (111)
Probable Mineral Reserve (121 & 122)

8. Why we calculate the resource and reserve?
The main aim of the entire geological activities is to quantify
the earth material including, rock, minerals, oil and Natural gas,
ground water etc. for the benefit of men kind.

Hence the process of sizing up of the ore body is known as the
resource/reserve estimation.

The estimation of resource means, to know the quality, quantity
and amenability to commercial exploration of the of raw
material, rock, ore, coal, oil, water etc.

The reserves are calculated to determine the extent of
exploration, development; distribution of values, daily and
annual out put, probable and possible productive life of the
mine.

9. Method of extraction, plant design treatment, processing,
requirement of capital, labour, power and to prepare the detail
raw material report of the project.

Resource estimation is a dynamic process as it is done at every
stage of geological work, from Preliminary to detailed
exploration stage, prospecting stage, deposit stage and mining
stage.

At different stage the confidence level of resource increases
from Preliminary exploration to mining stage.

10. Principles and assumptions in Resource estimation
Ore resource and grade estimation involves some unavoidable but un-
proveable assumptions based upon some accepted principles.
The principles are
The sampling procedure of any ore body is considered reliable and
random enough for calculation of sampling average which lead to
approximate deposit mean or population mean of the ore body.

Basic parameters of an ore body are established based upon point
estimates, such as sub-surface drill holes, surface sampling etc will
extend to the adjoining areas.

The common principles of rule of gradual change and rule of nearest
points have capability of generating realistic estimate in the matter of
ore volume computations.

11. The Rule of Gradual change or law of linear function.
According to this rule all elements or parameters of a mineral body
will change gradually and continuously along a straight line
connecting two adjoining stations, and which can be computed
mathematically or by graphic method.

Taking this assumption the grade, volume and thickness of the ore
can be calculated of any unknown point within the two blocks or
points of known value.
A B
t
1
t
2
Fig: Gradual variation of thickness from t
1 to t
2 from A to B

12. A B
T
a
T
b
C
T
c
d
2
Fig: Finding thickness at point C by graphical method. Thickness T
a and T
b
intersected in borehole A & B respectively. Measure the thickness T
c.
d
1

13. The following mathematical formula is used for finding
the grade, thickness and resource of the unknown points.
Gc=
Ga(d1) +Gb(d2)
(d1) + (d2)
Tc =
Ta(d1) + Tb( d2)
(d1) + (d2)
Rc =
Ra (d1) + Rb (d2)
(d1) + (d2)
Where
Gc= Grade at point C, unknown point
Ga = Grade at point A, known point.
Gb=Grade at point B, the known point.

d1= distance of point C from B
d2 = distance of point C from A.

Ta, Tb and Tc are the thickness at
points A, B and C similarly Ra, Rb and
Rc are the reserves at the point A,B,
and C respectively.

14. Rule of nearest points
This is also known as the rule of equal influence.

According to this rule the value of any point between two
stations is considered as constant, equal to the value of
nearest station.

As a general case the hole A and hole B with thickness t
1 and
t
2 respectively have the same value each one till the mid
point, i.e. it will be inside the area of influence of station A
and station B and near to it then to the adjoining one.

The rule of nearest point is used in construction of equal area
of influence for area and volume of individual intersections.
In most of the cases the rule of nearest point is used in
reserve/resource calculation.

15. M
1

A
B
M
t
1
t
2
Fig: Interpretation of values between two adjoining holes in section, M is mid
point and M- M
1 is middle line.

Rule of nearest points

16. Constraints of Rule of gradual change and nearest point
These rules have limitations in terms of Geological, mining and
economic considerations.

These rules should be adopted with modification in case of
geological boundaries due to structural features such as faults, folds,
change in strike and dip and other discontinuity.

Change in character of mineralization.

Thinning out or pinching out of ore shoots.

Zoning, weathering, different physical properties,
heterogeneous composition and varied alteration.

17. F
A
B
F
t
1
t
2
Fig: Area of influence between two boreholes or openings when geological
feature (F-F vertical fault) falls in between.

18. A
B
F
F
Fig: Area of influence on surface in either side of a fault.

19. Presumptions
Physical continuity of the ore body within the points of
testing and also beyond but disrupted by geological
discontinuities.

Nature of ore necessarily changes smoothly from point to
point in general pattern of sampling, geologically or
mathematically.

Characters of samples recovered to be representative in
spite of the known fact that the recovery, volume wise is
only 52.2 % but in NX size hole, under test conditions
assured 100% core recovery on the basis of length
parameters.

20. The ultimate objective of exploration is to compute
the resource of the mineral/ORE body and that includes
the following.

Objective of exploration
Determination of the quantity of the ore mineral.

Determination of quality and grade of the ore mineral.

Ascertaining the spatial distribution of the mineral in
deposit as a whole and in its separate blocks.

Reliability of the reserves, i.e. categorization of the
reserves.

21. Broadly the resources are classified in to two broad categories.

1.Geological Resources ( In-situ resources)
2.Mineable Resources

A.Industrial resource: Economically viable under the present
scenario with the available mining techniques,
beneficiation and smelting under present economic
conditions.

B.Non-industrial resources: Industrially important in future
when new mining, beneficiation and smelting methods are
developed or there is change in general economic
condition.

22. Mineralized zone: Mineralized zone can be defined as the zone within
the earth’s crust having the concentration of a particular element or
aggregate of elements more than background and threshold value of the
earth’s crust and the zone may be or may not be economically viable with
some given conditions.
Ore lode: Lode is that part of mineralized zone which have concentration
of an element more than the cut off of that particular element and which
can exploited economically.
RTRH-01/18 86.75 87.75 1.00 1.00 BDM+QBS 70 30
RTRH-01/19 87.75 88.75 1.00 1.00 QBS 60 30
RTRH-01/20 88.75 89.80 1.05 1.05 QBS 0.53% 30
RTRH-01/21 89.80 90.85 1.05 1.05 QBS 0.72% 30
RTRH-01/22 90.85 91.85 1.00 1.00 QBS 0.79% 30
RTRH-01/23 91.85 92.85 1.00 1.00 QBS 0.52% 30
RTRH-01/24 92.85 93.90 1.05 1.05 QBS 0.64% 30
RTRH-01/25 93.90 94.90 1.00 1.00 CQBS 0.73% 30
RTRH-01/26 94.90 95.95 1.05 1.05 CQBS 0.82% 30
RTRH-01/27 95.95 97.00 1.05 1.05 CQBS 0.26% 30
RTRH-01/28 97.00 98.00 1.00 1.00 BDM 0.10% 30
RTRH-01/29 98.00 99.00 1.00 1.00 BDM 0.05% 30
RTRH-01/30 99.00 100.00 1.00 1.00 BDM 0.27% 30
RTRH-01/31 100.00 101.00 1.00 1.00 BDM+QBS 520 30
RTRH-01/32 101.00 102.05 1.05 1.05 BDM+QBS 300 30
RTRH-01/33 102.05 103.10 1.05 1.05 BDM+QBS 390 30
RTRH-01/34 103.10 103.90 0.80 0.80 BDM+QBS 170 30

23. RTRH-02/53 113.20 113.90 0.70 0.70 BDM+QBS±Amp 390 30 50
RTRH-02/54 113.90 114.95 1.05 1.05 QBS 630 25 40
RTRH-02/55 114.95 116.00 1.05 1.05 QBS 0.41 25 50
RTRH-02/56 116.00 117.05 1.05 1.05 QBS 0.23 30 45
RTRH-02/57 117.05 118.10 1.05 1.05 QBS 0.24 30 40
RTRH-02/58 118.10 118.90 0.80 0.80 QBS 0.55 25 45
RTRH-02/59 118.90 119.70 0.80 0.80 QBS 0.48 20 40
RTRH-02/60 119.70 120.55 0.85 0.85 QBS 0.35 25 55
RTRH-02/61 120.55 121.55 1.00 1.00 QBS±Sc±Amp 0.26 25 60
RTRH-02/62 121.55 122.55 1.00 1.00 QBS±Sc±Amp 620 25 40
RTRH-02/63 122.55 123.55 1.00 1.00 QBS±Sc±Amp 0.12 25 45
RTRH-02/64 123.55 124.55 1.00 1.00 QBS±Sc±Amp 440 25 40
RTRH-02/65 124.55 125.55 1.00 1.00 QBS±Sc±Amp 200 25 45
RTRH-02/66 125.55 126.45 0.90 0.90 QBS±Sc±Amp 280 25 40
RTRH-02/67 126.45 127.45 1.00 1.00 QBS+DM±Sc±Amp 270 25 40
RTRH-02/68 127.45 128.45 1.00 1.00 QBS+DM±Sc±Amp 180 25 45
RTRH-02/69 128.45 129.45 1.00 1.00 QBS+DM±Sc±Amp 100 25 45
1 RTRH-06/01 53.00 54.00 1.00 1.00 QBS 600 30 50 30 150 <5 <5
2 RTRH-06/02 54.00 55.00 1.00 1.00 QBS 900 40 60 30 110 <5 <5
3 RTRH-06/34 55.00 56.00 1.00 1.00 QBS 110 30 60 40 100 <5 <5
4 RTRH-06/35 56.00 57.00 1.00 1.00 QBS 0.15% 30 50 40 110 <5 <5
5 RTRH-06/36 57.00 58.00 1.00 1.00 QBS 410 20 50 40 100 <5 <5
6 RTRH-06/03 58.00 59.00 1.00 1.00 QBS 0.62% 30 50 30 110 <5 <5
7 RTRH-06/04 59.00 60.00 1.00 1.00 QBS 0.32% 30 40 30 120 <5 <5
8 RTRH-06/05 60.00 61.00 1.00 1.00 QBS 0.33% 30 40 40 100 <5 <5
9 RTRH-06/37 61.00 62.00 1.00 1.00 Sc-Amp-QBS 0.56% 30 40 50 120 <5 <5
10 RTRH-06/38 62.00 63.00 1.00 1.00 Sc-Amp-QBS 0.46% 30 50 60 130 <5 <5
11 RTRH-06/39 63.00 64.00 1.00 0.95 Sc-Amp-QBS 0.53% 20 50 50 110 <5 <5
12 RTRH-06/40 64.00 65.00 1.00 1.00 Sc-Amp-QBS 0.38% 20 40 50 110 <5 <5
13 RTRH-06/41 65.00 66.00 1.00 1.00 Sc-Amp-QBS 0.29% 20 40 50 100 <5 <5
14 RTRH-06/42 66.00 67.00 1.00 1.00 Sc-Amp-QBS 680 20 40 60 130 <5 <5
15 RTRH-06/43 67.00 68.00 1.00 1.00 Amp-QBS 380 20 40 60 120 <5 <5
16 RTRH-06/44 68.00 69.00 1.00 1.00 Amp-QBS 240 20 40 70 150 <5 <5
17 RTRH-06/45 69.00 70.00 1.00 1.00 Amp-QBS 260 20 40 60 150 <5 <5
18 RTRH-06/06 70.00 71.00 1.00 1.00 Sc-DM 330 30 50 40 180 <5 <5
19 RTRH-06/07 71.00 72.00 1.00 1.00 Sc-DM 310 30 50 50 130 <5 <5
20 RTRH-06/08 72.00 73.00 1.00 1.00 Sc-DM 200 30 50 40 110 <5 <5
21 RTRH-06/09 73.00 74.00 1.00 1.00 Sc-DM±Amp 210 30 50 40 140 <5 <5

24. S. No. Ref. No.
Depth (m) Core
Recovery
Cu (%)
Cu
ppm
Co
ppm
Ni ppm
Pb
ppm
Zn ppm
Ag
ppm
Cd
ppm From To Length
22 RTRH-06/10 74.00 75.00 1.00 1.00 210 30 50 50 130 <5 <5
23 RTRH-06/11 75.00 76.00 1.00 1.00 300 20 40 30 130 <5 <5
24 RTRH-06/12 76.00 77.00 1.10 0.95 0.21% 20 40 40 90 <5 <5
25 RTRH-06/13 77.00 78.00 1.00 1.00 0.67% 20 40 30 80 <5 <5
26 RTRH-06/14 78.00 79.00 1.10 1.10 0.91% 20 40 50 70 <5 <5
27 RTRH-06/15 79.00 80.00 0.90 0.90 0.74% 30 40 40 90 <5 <5
28 RTRH-06/16 80.00 81.00 1.00 1.00 0.82% 30 50 40 130 <5 <5
29 RTRH-06/17 81.00 82.00 1.05 1.05 0.23% 30 50 40 120 <5 <5
30 RTRH-06/18 82.00 83.00 1.20 1.15 0.13% 30 40 40 130 <5 <5
31 RTRH-06/19 83.00 84.00 1.00 1.00 0.01% 140 30 50 60 160 <5 <5
32 RTRH-06/20 84.00 85.00 1.10 1.10 0.35% 30 50 60 140 <5 <5
33 RTRH-06/21 85.00 86.00 1.00 1.00 230 30 50 70 180 <5 <5
34 RTRH-06/22 86.00 87.00 1.00 1.00 210 30 60 60 190 <5 <5
35 RTRH-06/23 87.00 88.00 1.00 1.00 110 30 50 70 170 <5 <5
36 RTRH-06/24 88.00 89.00 1.00 1.00 140 30 40 60 110 <5 <5
37 RTRH-06/25 89.00 90.00 1.00 1.00 110 30 50 60 170 <5 <5
38 RTRH-06/26 90.00 91.00 1.00 1.00 0.13% 30 50 60 170 <5 <5
39 RTRH-06/27 91.00 92.00 1.00 1.00 0.27% 30 50 50 130 <5 <5
40 RTRH-06/28 92.00 93.00 1.00 1.00 510 30 40 50 80 <5 <5
41 RTRH-06/29 93.00 94.00 1.00 1.00 180 20 40 50 90 <5 <5
42 RTRH-06/30 94.00 95.00 1.00 1.00 120 30 50 60 130 <5 <5
43 RTRH-06/31 97.00 98.00 1.00 1.00 270 30 50 70 120 <5 <5
44 RTRH-06/32 106.00 107.00 1.00 1.00 520 30 40 70 130 <5 <5
45 RTRH-06/33 117.00 118.00 1.00 1.00 720 30 50 60 170 <5 <5

25. Resource is determined by multiplying the volume of the
ore body by the bulk density.

Parameters for calculation of resource
1.Cut off grade
2.Stopping width
3.Weighted average and average grade
4.Tonnage factor
5.Core recovery
6.Thickness of the ore body
7.Strike influence or Strike length
8.Dip length or dip influence
9.Correlation of lode.

26. Cut off grade
Cut off grade is mainly depends upon the following factors
Economic scenario of an area.
The country.
International market
Value of a particular mineral
Strategic mineral
Nature of deposit
Nature of occurrence
Beneficiation techniques
Method of mining
Requirement of industries.

27. Natural cut off: the cut off which is taken directly from the mine
Without admixing is known as natural cut off.
Ct=
Pc
Vm
X 100
Cut off can be determined by the following formula:
Ct = Cut off grade
Pc = Production cost
Vm = Value of mineral content
Cut off grade for different commodity is different. For example:
Commodity Cut off grade
Copper (Cu) 0.20% (IBM Guideline)
Gold (Au) 0.5ppm
Silver (Ag) 5.0ppm
Lead (Pb) 4.0%
Cut off grade changes
with time, with the
development of modern
technology and socio-
economic condition of a
country.

28. Stopping width
Minimum width or thickness required for mining of an ore body.
For underground mining method minimum stopping width is taken as 2.0m
Weighted average and average grade
Vta =
∑ Ls *As
∑ Ls
Vta= Weighted average grade
Ls= Length of sample
As= Assay of samples
Agr =
Wta
1 x t
1+ Wta
2 x t
2+ Wta
3 x t
3
t
1+ t
2+ t
3
Wta
1= Weighted average of lode no 1
t
1 = Thickness of lode no.1
Agr = Average grade

29. S. No. Ref. No.
Depth (m) Core
Recovery
Cu (%)
Cu
ppm
Co
ppm
Ni
ppm
Pb
ppm
Zn
ppm
Ag
ppm
Cd
ppm From To Length
22 RTRH-06/10 74.00 75.00 1.00 1.00 210 30 50 50 130 <5 <5
23 RTRH-06/11 75.00 76.00 1.00 1.00 300 20 40 30 130 <5 <5
24 RTRH-06/12 76.00 77.00 1.10 0.95 0.21% 20 40 40 90 <5 <5
25 RTRH-06/13 77.00 78.00 1.00 1.00 0.67% 20 40 30 80 <5 <5
26 RTRH-06/14 78.00 79.00 1.10 1.10 0.91% 20 40 50 70 <5 <5
27 RTRH-06/15 79.00 80.00 0.90 0.90 0.74% 30 40 40 90 <5 <5
28 RTRH-06/16 80.00 81.00 1.00 1.00 0.82% 30 50 40 130 <5 <5
29 RTRH-06/17 81.00 82.00 1.05 1.05 0.23% 30 50 40 120 <5 <5
30 RTRH-06/18 82.00 83.00 1.20 1.15 0.13% 30 40 40 130 <5 <5
31 RTRH-06/19 83.00 84.00 1.00 1.00 0.01% 140 30 50 60 160 <5 <5
32 RTRH-06/20 84.00 85.00 1.10 1.10 0.35% 30 50 60 140 <5 <5
33 RTRH-06/21 85.00 86.00 1.00 1.00 230 30 50 70 180 <5 <5
34 RTRH-06/22 86.00 87.00 1.00 1.00 210 30 60 60 190 <5 <5
35 RTRH-06/23 87.00 88.00 1.00 1.00 110 30 50 70 170 <5 <5
36 RTRH-06/24 88.00 89.00 1.00 1.00 140 30 40 60 110 <5 <5
37 RTRH-06/25 89.00 90.00 1.00 1.00 110 30 50 60 170 <5 <5
38 RTRH-06/26 90.00 91.00 1.00 1.00 0.13% 30 50 60 170 <5 <5
39 RTRH-06/27 91.00 92.00 1.00 1.00 0.27% 30 50 50 130 <5 <5
40 RTRH-06/28 92.00 93.00 1.00 1.00 510 30 40 50 80 <5 <5
41 RTRH-06/29 93.00 94.00 1.00 1.00 180 20 40 50 90 <5 <5
42 RTRH-06/30 94.00 95.00 1.00 1.00 120 30 50 60 130 <5 <5
43 RTRH-06/31 97.00 98.00 1.00 1.00 270 30 50 70 120 <5 <5
44 RTRH-06/32 106.00 107.00 1.00 1.00 520 30 40 70 130 <5 <5
45 RTRH-06/33 117.00 118.00 1.00 1.00 720 30 50 60 170 <5 <5
Calculate weighted average grade of Cu from the following assay values of Cu

30. Tonnage factor
The tonnage factor or bulk density is a multiplier to the volume for the
determination of resource.
Bulk density can be determined by two methods
A.Cubical Opening method: Dig up a pit of 1m x 1m size and weight all the
material(rock, mineral). The weight is the tonnage factor.
B.Conventional density measurement method: the density of samples
determined by measuring the weight and volume of the samples by
traditional method.
D=W/V D= Density, W= weight, V= Volume
D=W1/W1-W2
W1= Weight in air
W2= Wight in water
C. Determination of Bulk Density by using drill cores: The bulk density
can be determined by measuring the length of core or half core.
V=π R
2
L (If the core is not spitted)
V=1/2π R
2
L (If the core is spitted)
V=Volume, R= Radius of core sample,
L= length of core sample

31. Core recovery
Core recovery play an very important role in computation of ore
resources, therefore, the core recovery should be very high, at least in
the mineralized zone.
Core Recovery= L1/L * 100, where L1= core recovered and L= Run length
If Recovery is >95%, For resource calculation it may be taken as 100%
If recovery is <95%, Correction factor have to be applied while
calculation of thickness of lode.
A.Dilution method: Assay value of recovered core is distributed in the
whole run assuming that the part of core which is not recovered was
barren. By this method grade will go down the assay value (recovery
should be >90%).

Gr= A* L1/L where Gr= Grade, A= Assay value of sample.

32. B. Reduced width method: In this case core loss is considered as voids
and the lode width is taken as the length of the core recovered.
Thickness of lode will reduce but grade will be as per assay value.


C. Equal grade method: If core recovery >90% or =95%, the grade of
recovered length is taken as the grade of run with assumptions that
the uncovered portion also contain the same assay value.

33. Thickness of the ore body
Thickness: Thickness of the ore body is determined by computing the
thickness of the lode in individual borehole after giving angle correction to
determine true thickness.
S80E
N80W
Zenith
BH-1
BH-2
N
Azimuth
Strike
Fig: A shows BH-1 intersecting the ore body perpendicularly and B shows the
BH-2 is perpendicular to the strike of the ore body.
A
B
Tr
Th
Tr
Tr= True thickness
Th= Horizontal thickness
1. Azimuth and zenith perpendicular to strike and dip plane.

34. 2. Azimuth perpendicular to the strike and zenith oblique to dip plane.
In case of inclined borehole

Tr = Ta Sinβ

Where,
Tr = True thickness
Ta = Apparent thickness
β = Core angle

S80E
N80W
Zenith
BH-1
Azimuth
Tr
Ta
90⁰
β
Th
β
α
α
Th = Tr/ Sinα

Th = Horizontal thickness
α = Dip of Mineralized zone

35. Strike influence or Strike length
Strike Influence: It is determined on the basis of openings along
the strike of the ore body. In case of co-relatable lode the strike
influence is taken as half the distance between the two boreholes
or openings.
Dip length Influence: Dip length influence for each borehole is
taken as half the distance between the adjacent boreholes in case
of inclined ore body, if the ore body have been intersected at
different levels.
Dip length influence

36. Strike length/ strike influence
The strike length is determined on the basis of boreholes
drilled along the strike of the ore body.

The strike influence of each borehole is determined on the
basis of nearest point and gradual variation.

In case of co-relatable lode the strike influence is taken as
half the distance between two borehole.

In non-corelatable lode also the distance along strike is
taken as half the distance between two points or less than
that depending upon the variation of the ore body.

37. Strike length Influence
Geological map
300m
500m
100m
Dolomite Lode Schist
N
E
Distance
Distance
Bore hole
X-3
X-2
X-1
N

38. 150 50 100 200 250 m
N
0 m 20 m
Scale (1:1000)
200 m
100 m
300 m
400 m
500 m
00 m
250 m Distance in m
Distance in m

X-1
X-3
X-2
N
E
W
S
0 0 0
0 0 0 0
0 0 0 0
BH-3
BH-2 BH-1
BH-4
BH-5 BH-6
INDEX
SURFACE GEOLOGICAL MAP OF BLOCK ‘A’
0
0
0

39. Dip Length/ Dip Influence
► Like strike influence the dip length influence, for
each borehole is also taken as half the distance
between the adjacent borehole in the case of inclined
ore body and if the ore body have been intersected at
different level.
►For inferred category (G3), down dip length
influence is taken 50% of adjacent opening.
►For indicated category (G2), down dip length
influence is taken 25% of adjacent opening.

40. 100m
200m
400m
BH-3
BH-4
S80E
N80W
Y1
Y1
Fig: Cross section of BH-3 & BH-4 showing influence of dip length, Y1+Y1=2Y1 for
each intersection.

41. E
Geological cross section along Line – X1
W
50 m
BH-3
BH-4
100 m
200 m
150 m
250 m
350 m
300 m
50 m 100 m 150 m 300 m 250 m 200 m
0 m
Pr
Po
Pr
Po
Inf
RL
RL
RL
RL

42. ► For the computation of the resource by cross
section of each borehole the volume is determined by
multiplying the (1) strike influence with (2) dip
length influence and (3) true thickness intersected/
calculated.

43. ORE RESOURCE CALCULATION METHODS
For homogeneous bedded horizontal or low dipping deposits  Included area method
 Extended area method
 Triangle method
 Polygon method
 Method of isoline
 Isopach maps method
For moderately to steeply dipping ore body
 Cross section method
 Longitudinal section method
 Level plan method

44. GRID PATTERN AND INCLUDED AREA METHOD
1.This method is adopted where the opening samples or boreholes drilling is
done along a rectangular or square grid pattern.
2. In this method one rectangle or square of the grid is taken and the thickness
is computed of the centre point of the grid by taking the average of thickness
of all the four boreholes ( at the corner of the rectangle of square).

Thickness= T1+ T2+T3+T4
4

Average grade Gav= T1 C1+ T2C2+ T3C3+T4C4
T1+ T2+ T3+T4
C1,C2,C3 and C4 are the assay value of the lode intersected in each
borehole.

45. GRID PATTERN AND INCLUDED AREA METHOD

46. Grid pattern and Included area method
Volume (V) = X x Y x T
Reserve of one rectangle or square (R) = V x Bd
Bd = Bulk density
GRID PATTERN EXTENDED AREA METHOD
1.In this method, the area of influence is taken around the
opening, thus constructing a rectangle keeping opening at
the centre of the rectangle.
2.The thickness intersected become the thickness of the
rectangle and resource of each rectangle is as follow and
grade remain as intersected in the borehole.

47. Volume (V) = ST,
where T = Thickness of borehole
S= Area of rectangle
Reserve of one block of rectangle
R= V X Bd = SXTX Bd
Reserve of total deposit (Re) = R1+ R2+ R3
Grade of the deposit= R1G1+ R2G2+ R3G3+
R1 + R2 + R3 ---
G1,G2,G3 is the grade of each rectangle or block
R1,R2,R3 is the reserve of each rectangle or block
Grid pattern extended area method cont-

48. Grid pattern extended area method

49. Cross section method
The cross-section or traverse section prepared across the ore body
represent the actual geological features in shape and quality
For the calculation of the reserve by this method the area of
influence and quality is considered on the basis of the rule of
nearest point
In the cross section area method the reserve is calculated for
individual opening and the area of influence of that opening is
measured on the cross section or calculated by measuring actual
thickness and dip length.
RL in
mt.
Bore hole 1
Dolomite
Lode
Bore hole 2
180
188
171
164

51. B
h
N
o
.
App.
Thic
knes
s
Angle
of lode
with
core
axis
True
thickne
ss
Core
recover
y
%C
u
Lode RL Dip
Length
Dip RL Strike
length
Tonn
age
factor
cate
gory
Tonnage
T*DL*SL
*TF in
tonnes
Total
reser
ve
Upp
er
Low
er
Uppe
r
Low
er
1 12m 78⁰ 11.5 100% 2 180
m
171
m
31 188
m
164
m
200m 2.5 Prob
able
186000

52. Longitudinal vertical projected section method
This method is very helpful in correlating the ore body along the strike
This method is very useful in determining the resurce of complex ore body.
In longitudinal vertical projected section the RL of the intersection of the
ore body is projected on any vertical plane parallel to the strike of the ore
body and lodes are correlated.
In this area of influence is taken half the distance between openings and
that is measured on the section or computed by multiplying the X and Y.
X-1
X-2 X-3
BH1
BH2
RL in
mt.
100
500

53. ► For the computation of the resource by LV section
of each borehole the volume is determined by
multiplying the

(1) strike influence with (2) difference in dip length
R.L. and (3) horizontal width measured.

56. Level plan method
Level plan is prepared by plotting of the lode intersection on a
horizontal plan passing through the level of intersection or at particular
RL. It represents the lode at that particular level.

300m
100m
Dolomite Lode Schist
E
Distance
Bore hole
Geological map
X-2
X-1
X-3
BH1 BH2
BH3 BH4
BH5 BH6

57. Methods of resource estimation

The resource for strata-bound dipping ore bodies are calculate by

1.Geological Cross section method

Cross section method, formula for calculating resource is
Tonnage = Strike length X Dip Length X True thickness
X Specific gravity
2. Longitudinal vertical section (LVS)method.

Formula for calculating resource in LVS method

Tonnage = Strike length X Difference in dip RL
X Horizontal thickness X Specific gravity

58. Thank you……