Calcite is calcium carbonate and fizzes in acid. It is usually white or colorless, but can be other colors because of impurities in it. It may have many outward shapes, but always breaks into little pieces shaped like rhombs. Calcite makes up the rock called LIMESTONE and is used to make cement, as fertilizer and as building stones.

Dolomite is a calcium-magnesium carbonate and fizzes in warm acid. It is usually pink or white and has curved faces. Dolomite is limestone with magnesium added. It is used for building stones and for making refractory bricks for furnace linings.

-drawings by Darryl Powell

Fluorite is calcium fluoride. It will change color under fluorescent light and this property is called fluorescence. It is usually purple, light-green, yellow or clear. It forms in cubes. It is used for a flux in smelting iron, for decorative stones, in the chemical industry and for making optical equipment.

Pyrite is iron sulfide. It is also called fool's gold because it is a metallic gold color. Sparks will fly if it is hit with a hammer. It forms in cubes. It is not valuable by itself, but is often rich in gold and copper. Fossils are often replaced by pyrite.