The various size classifications are based on the deposit’s “pre-mined resource”. This is the current published Measured, Indicated & Inferred Resource (as defined by JORC) plus cumulative historic production (adjusted for mining and processing losses).
>6Moz Au, >1Mt Ni, >12 Mt Zn+Pb, >300Moz Ag, >1000 Mt thermal coal, >500 Mt coking coal, >500 Mt Fe, >125 kt U3O8, and >5Mt Cu or its equivalent in-situ value for other metals
1-6Moz Au, 0.1-1Mt Ni, 2.5-12 Mt Zn+Pb, 50-300Moz Ag, 200-1000 Mt thermal coal, 100-500 Mt coking coal, 100-500 Mt Fe, 25-125 kt U3O8, and 1-5Mt Cu or its equivalent in-situ value for other metals
100koz-1Moz Au, 10-100kt Ni, 250kt-2.5Mt Zn+Pb, 5-50Moz Ag, 20-200 Mt thermal coal, 10-100 Mt coking coal, 10-100 Mt Fe, 5-25kt U3O8, and 1-5Mt Cu or its equivalent in-situ value for other metals
10-100koz Au, 1-10Kt Ni, 25-250kt Zn+Pb, 0.5-5Moz Ag, 2-20 Mt thermal coal, 1-10 Mt coking coal, 1-10 Mt Fe, 0.5-5kt U3O8, and 10-100kt Cu or its equivalent in-situ value for other metals.
In situations where a JORC-defined Resource has not been reported, the author made a judgment call on the general size range of the deposit.
For purposes of this study a “significant” deposit is defined as one that is >=“Moderate-sized”.