[3][5] Smithsonite is a variably colored trigonal mineral which only rarely is found in well formed crystals.

Smithsonite occurs as a secondary mineral in the weathering or oxidation zone of zinc-bearing ore deposits.

It sometimes occurs as replacement bodies in carbonate rocks and as such may constitute zinc ore.

It commonly occurs in association with hemimorphite, willemite, hydrozincite, cerussite, malachite, azurite, aurichalcite and anglesite.

The cause of the yellow colour is due to the presence of greenockite inclusions within the smithsonite crystals.