accessory mineral

noun

Petrography.

a mineral that is present in small amounts in a rock and has no bearing on the classification of the rock, as zircon in granite.

accessory mineral

A mineral that is present in a minor amount in rocks and is not considered an essential constituent of the rock.

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It is frequently present as an accessory mineral in sulphide deposits containing ores of gold, copper, silver, lead, and zinc.