🔹 1. Introduction 

Ore Reserve Estimation is the foundation of mine planning, determining:

• Mine life
• Economic feasibility
• Production strategy
• Equipment selection
• Long-term investment planning

Accurate reserve estimation is mandatory under DGMS and UNFC guidelines for every mining lease.
Poor estimation can lead to:

• Overestimation → financial losses
• Underestimation → loss of valuable reserves
• Wrong mine design → slope failures, early closure

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🔹 2. Key Definitions 

  ⭐ Ore Naturally occurring mineral deposit that can be mined profitably. 

  ⭐ Mineral Resources Total mineralization (economic + uneconomic). 

⭐ Ore Reserves Economically extractable portion of the mineral resource. 

⭐ Cut-off Grade Minimum grade required for profitable mining.

⭐ Tonnage Total mass of mineralized material.

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🔹 3. Steps in Ore Reserve Estimation

1. Geological mapping
2. Sampling
3. Assay analysis
4. Grade interpolation
5. 3D block modelling
6. Volume calculation
7. Tonnage calculation
8. Reserve classification (UNFC/DGMS)
9. Reporting

🔹 4. Sampling Methods in Mining

Sampling must be representative, unbiased, and systematic.

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⭐ 1) Channel Sampling

• Cut channels across ore body
• Best for narrow veins
• High reliability

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⭐ 2) Chip Sampling

• Small fragments collected from face
• Medium accuracy

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⭐ 3) Grab Sampling

• Material picked randomly
• Least reliable
• Only for preliminary assessment

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⭐ 4) Core Drilling Samples

• Diamond drilling
• Continuous record of rock
• Most trusted for depth continuity

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⭐ 5) Bulk Sampling

• Large quantity (100–1000 kg)
• Used for metallurgical testing

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⭐ 6) Trench & Pit Sampling

• Surface deposits
• Weathered zones

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⭐ 7) Blast Hole Sampling 

 Used in open pits for:

• Grade control
• Ore/waste boundary marking

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🔹 5. Sample Preparation & Assay 

 Before chemical analysis, samples undergo:

• Drying
• Crushing
• Splitting (riffling)
• Pulverizing
• Chemical assay

Assay Methods:

• Fire Assay (Gold)
• XRF
• Wet chemical analysis
• AAS

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🔹 6. Reserve Estimation Methods

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⭐ A. Cross-Sectional Method

(A1 & A2 = cross-section areas; L = distance between them)

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⭐ B. Triangular Method

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⭐ C. Polygon (Area of Influence) Method Each sample point has polygon-shaped influence.

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⭐ D. Trapezoidal Method Used for irregular shapes.

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⭐ E. Block Modelling (3D Digital Model) Most widely used modern method. Mine area is divided into 3D blocks (e.g., 10m × 10m × 10m).
Each block contains:

• Volume
• Density
• Grade
• Coordinates
• Rock type

Modelling software:
Surpac, Datamine, Whittle, MineSched

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⭐ F. Inverse Distance Weighting (IDW) Grade of block depends on inverse distance from samples.

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⭐ G. Ordinary Kriging (Geostatistics) Most accurate & scientific method.
Uses variogram to predict grade between distant samples.

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🔹 7. Tonnage Calculation

Where:

• Volume (m³)
• Density (t/m³)

Example:
Volume = 25,000 m³
Density = 2.6 t/m³
Tonnage = 65,000 tonnes

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🔹 8. Grade Estimation 

  ⭐ Weighted Average Grade

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🔹 9. Dilution & Recovery 

  ⭐ Dilution Waste mixed with ore during mining.

⭐ Recovery Percentage of ore actually extracted.

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🔹 10. UNFC / DGMS Reserve Classification 

  ⭐ 111 – Proved Reserve (Measured) High confidence. 

  ⭐ 121 / 122 – Probable Reserve (Indicated) Medium confidence. 

  ⭐ 333 – Possible (Inferred Resource) Low confidence.

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🔹 11. Grade Control in Surface Mining

• Blast hole sampling
• Ore/waste boundary mapping
• GPS-based ore routing
• Stockpile blending
• On-belt analyzers

Grade control ensures the ROM (Run of Mine) meets:

• Fe%, Al%, SiO₂%, Coal GCV, Ash%
• Customer specifications
• Beneficiation requirements

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🔹 12. Applications of Reserve Estimation in Mine Planning

• Production planning
• Mine life calculation
• Equipment requirement
• Economic feasibility
• Cut-off grade decision
• Waste/OB planning

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🔹 13. Text Diagram – Block Model Concept +--------+--------+--------+ | Block1 | Block2 | Block3 | +--------+--------+--------+ | Block4 | Block5 | Block6 | +--------+--------+--------+ | Block7 | Block8 | Block9 | +--------+--------+--------+ Each block contains: Grade | Density | Volume | Coordinates

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🔥  25 MCQs (DGMS Pattern) with Answers

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1) Ore reserve refers to —

a) All minerals
b) Soil cover
c) Economically mineable part of resource
d) Waste rock
e) None
Ans: c

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2) Tonnage = Volume × ?

a) Angle
b) Area
c) Density
d) Height
e) None
Ans: c

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3) Most reliable sampling method —

a) Grab
b) Chip
c) Core drilling
d) Hand picking
e) None
Ans: c

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4) Triangular method includes —

a) RL
b) √(A1 × A2)
c) Wind factor
d) Slope
e) None
Ans: b

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5) Variogram is used in —

a) Geometry
b) Kriging
c) Drilling
d) Haulage
e) None
Ans: b

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6) Block model uses —

a) 2D planes
b) 3D blocks
c) Road designs
d) Blasting patterns
e) None
Ans: b

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7) Dilution means —

a) Adding water
b) Mixing waste with ore
c) Adding explosives
d) Reducing grade
e) None
Ans: b

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8) Grab sampling is —

a) Best
b) Least reliable
c) Same as channel
d) Core drilling
e) None
Ans: b

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9) Weighted average grade used for —

a) Coal quality
b) Multiple sample analysis
c) Water measurement
d) Gas
e) None
Ans: b

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10) UNFC code for proved reserve — 

a) 333
b) 211
c) 111
d) 323
e) None
Ans: c

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11) Blast hole sampling used for —

a) Ventilation
b) Noise
c) Grade control
d) Drainage
e) None
Ans: c

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12) Ore recovery reduces when —

a) Good fragmentation
b) High dilution
c) Short benches
d) Optimal blasting
e) None
Ans: b

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13) Cross-sectional method uses —

a) Weather data
b) Colour
c) Area of sections
d) Gas reports
e) None
Ans: c

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14) Density given in —

a) m³/t
b) g/litre
c) t/m³
d) cm²
e) None
Ans: c

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15) Most inaccurate sampling —

a) Channel
b) Chip
c) Grab
d) Grab
e) None
Ans: d

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16) Cut-off grade determines —

a) Working hours
b) Economic viability
c) Water inflow
d) Tyre pressure
e) None
Ans: b

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17) Block model commonly used in —

a) Roadworks
b) Modern mine planning software
c) Ventilation
d) Fire fighting
e) None
Ans: b

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18) Fire assay used for —

a) Coal
b) Iron ore
c) Gold
d) Limestone
e) None
Ans: c

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19) UNFC 333 represents —

a) Measured
b) Indicated
c) Inferred
d) Proven
e) None
Ans: c

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20) Best for ore/waste boundary —

a) Magnet
b) Blast hole sampling
c) Wind compass
d) Tape
e) None
Ans: b

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21) High dilution results in —

a) Profit
b) High grade
c) Low grade & loss
d) Clean ore
e) None
Ans: c

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22) Core samples obtained from —

a) Explosives
b) Trucks
c) Diamond drills
d) Shovels
e) None
Ans: c

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23) Reserve estimation regulates —

a) Weather
b) Mine life & production
c) Ventilation
d) Lighting
e) None
Ans: b

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24) Bulk sampling used for —

a) Gas detection
b) Metallurgical testing
c) Dump design
d) Haul roads
e) None
Ans: b

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25) Best method for modern mines —

a) Hand sampling
b) Grid sampling
c) 3D block model
d) Compass
e) None
Ans: c

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🔚 Conclusion 

Ore Reserve Estimation is the backbone of mining economics.

With proper sampling, accurate assays, scientific modelling and DGMS-compliant classification, mines achieve:

• Accurate mine life
• Reliable production planning
• Correct equipment sizing
• Minimum dilution losses
• Consistent grade control

A precise reserve estimate ensures both economic success & statutory compliance.

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