Minerals and Ore Grades Quiz

Mineral Definition

• Naturally occurring, inorganic, homogenous solid with a definite chemical composition and ordered internal structure (Crystalline)
• Rock: Any naturally formed aggregate of one or more types of mineral particles

Rules Of Thumb Grades Of Ore

• Gold
  • Low grade: 0–0.5 g/t (Open Pit), 0–5.0 g/t (Underground)
  • Average grade: 0.5–1.5 g/t (Open Pit), 5.0–8.0 g/t (Underground)
  • High grade: over 1.5 g/t (Open Pit), over 8.0 g/t (Underground)
• Silver
  • Low grade: 0–30 g/t (Open Pit), 0–150 g/t (Underground)
  • Average grade: 30–150 g/t (Open Pit), 150–350 g/t (Underground)
  • High grade: over 150 g/t (Open Pit), over 350 g/t (Underground)
• Copper
  • Low grade: 0–0.5% (Open Pit), 0–1.0% (Underground)
  • Average grade: 0.5–1.0% (Open Pit), 1.0– 3.0% (Underground)
  • High grade: over 1.0% (Open Pit), over 3.0% (Underground)

Tonnage Definition

• Expression of the amount of material of interest irrespective of the units of measurement

Recovery Definition

• Percentage of material of initial interest that is extracted during mining and/or processing
• A measure of mining or processing efficiency

Mineral Resource vs Ore Reserve (PMRC 2007)

• Mineral Resource: a concentration or occurrence of material of intrinsic economic interest in or on the Earth’s crust in such form, quality and quantity that there are reasonable prospects for eventual economic extraction
• Ore Reserve: economically mineable part of a Measured and/or Indicated Mineral Resource; includes diluting materials and allowances for losses, which may occur when the material is mined.

Mineral Resource vs Mineral* Reserve (PMRC 2020)

• Mineral Resource: a concentration or occurrence of solid material of intrinsic economic interest in or on the Earth’s crust in such form, grade (or quality) and quantity that there are reasonable prospects for eventual economic extraction
• Mineral Reserve*: economically mineable part of a Measured and/or Indicated Mineral Resource; includes diluting materials and allowances for losses, which may occur when the material is mined or extracted and is defined by Pre-feasibility or Feasibility studies

Mineral Resource Categories (PMRC 2020)

• Inferred: quantity & grade are estimated on the basis of limited geological evidence and sampling
• Indicated: densities, shape, and physical characteristics are estimated with sufficient confidence to allow the application of Modifying Factors to support mine planning and economic viability evaluation
• Measured: densities, shape, and physical characteristics are estimated with confidence sufficient to allow the application of Modifying Factors to support detailed mine planning and final economic viability evaluation

Ore Reserve Categories (PMRC 2007)

• Probable: economically mineable part of an Indicated, and in some circumstances, a Measured Mineral Resource
• Proved: economically mineable part of a Measured Mineral Resource

Mineral* Reserve Categories (PMRC 2020)

• Probable: economically mineable part of an Indicated, and in some circumstances, a Measured Mineral Resource
• Proved: economically mineable part of a Measured Mineral Resource. It implies TECHNICAL STUDIES

Gross Value And Profit Calculations

• Gross Value = Grade (% or g/MT) x Recovery (%) x Price ($)
• Profit = Gross Value – Cost
• Example: Estimate the unit profit in $/ton of mining and processing a copper ore body averaging 0.60% by weight Cu if the selling price of copper in the concentrate is $4.2/lb, assuming that the overall cost of mining and processing is $6.80/ton. Overall recovery, based on metallurgical engineering is expected to be 92% of the copper.
  • Gross Value = 0.006 x 0.92 x $4.2/lb x 2000lbs/ton = $ 46.368/ton
  • Profit = $46.368/ton - $6.80/ton = $ 39.568/ton