The enrichment factor represents the relative concentration of an element or mineral in a particular area as compared to its average abundance in the Earth's crust. For a mineral ore, the enrichment factor must be high enough to make mining profitable. In this case, the enrichment factor is the ratio between the minimum profitable (or cut-off) grade and the average crustal abundance.

Formula used to determine Enrichment Factor:

For example, Lead composes 0.0013% of the Earth's crust and it's accepted minimum grade is 4%. 4/0.0013 = ~3,100, therefore Lead's enrichment factor is 3,100.

Minimum Grade (%) / Crustal Abundance (%) = Enrichment Factor