What mineral is described below? (Feel free to use the Mineral Key.) - White and glassy in appearance - Mass = 54 grams - Volume = 20 milliliters - Scratches a fingernail but not a penny - White streak - Fizzes in acid

The mineral is calcite.

Lustre - glassy; ∴ non-metallic

Hardness - between a fingernail (2.5) and a penny (3)

Streak - white

Specific gravity - 54/20 = 2.7

Colour - white

Acid reaction - Fizzes; ∴ a carbonate

The only carbonate mineral that satisfies all these criteria is calcite, CaCO₃.