Mining & Mineral Economics

Resource & Reserve Classification

Turning a measured deposit into tonnage: in-situ mass from geometry and density, then recoverable reserve after mining losses.

PART 1

Topic Breakdown & Traps

The Engineering Principle

A mineral resource becomes a reserve once economic and technical modifying factors are applied. The in-situ tonnage of a tabular deposit is its area times thickness times density. The recoverable reserve is that in-situ tonnage multiplied by the recovery factor — the fraction the chosen method can actually extract. Confidence levels (measured/indicated/inferred) classify how well the geometry and grade are known.

The Core Formula Matrix

In-situ tonnage:

T = A \times t \times ρ

(

A

= area,

t

= thickness,

ρ

= density).

Recoverable reserve:

T_{r ec} = T \times R

(

R

= recovery factor).

The ‘IIT Traps’

⚠
Keep units consistent: area in m², thickness in m, density in t/m³ ⇒ tonnes.
⚠
Resource ≠ reserve. Reserve is what's economically recoverable, after the recovery factor.
⚠
Apply recovery to in-situ tonnage, not the other way round.

PART 2

Progressive 3-Tier Question Suite

Q1BASIC1 Mark · MCQ

A tabular orebody covers

50, 000 m^{2}

, is

4 m

thick, density

2.5 t/m^{3}

. Its in-situ tonnage is:

Q2MEDIUM2 Marks · NAT

If that

500, 000 t

in-situ deposit is mined at

80%

recovery, the recoverable reserve is ______ tonnes. (Round off to the nearest whole number.)

Q3HARD2 Marks · NAT

A proved block of area

120, 000 m^{2}

, average thickness

3.5 m

, density

2.7 t/m^{3}

is mined at

75%

recovery. The recoverable reserve is ______ tonnes. (Round off to the nearest whole number.)