Galena and Calcite

Galena

Galena generally occurs as cubic crystals, typically lead grey in colour. There are also frequent cases in which it occurs in granular, compact masses, very shiny on the surface. The colour that characterises it, in the streak too, is lead grey. Galena is soft, heavy and brittle, it is soluble in hydrochloric acid, producing hydrogen sulphide.

The most common places of formation are hydrothermal veins and sedimentary and metamorphic environments.

The main use of galena is industrial, for the extraction of lead. Silver can be obtained from some argentiferous minerals.

Calcite

Calcite forms crystals of very different shapes: rhombohedral, prismatic, tabular, etc. There are also cases in which it occurs as granular, lamellar, parallel or columnar aggregates. Often colourless or whitish, calcite can also form crystals of various colours: pinkish, yellow, brown or green. It has a vitreous to pearly lustre, with semi-hard, light crystals, soluble in cold hydrochloric acid.

Calcite is typically sedimentary in formation, of chemical or organic formation. It can sometimes also have a metamorphic origin or form in hydrothermal veins, and rarely a magmatic one.

It is used in the chemical, metallurgical, in building and in sculpture