How are Minerals Identified?

Minerals and how they form A Mineral is a naturally formed, nonliving solid that has a crystalline or repeating, structure. Mineral crystals can form deep within Earth, in caves, from seawater, in underground water.

Minerals also form inside geodes. Geodes are dull on the outside but inside has crystals that may be bright.

Color and Streak Salt Minerals: Rubies, quartz Metal Minerals: Copper, silver, gold Scientists identify minerals by using their properties.

Streak is the color of the powder left behind when a mineral rubbed against a streak plate. A streak plate is a rough white tile. Minerals can change color if exposed to air or rain for a long time.

Luster, Cleavage, and Fracture The way that a mineral’s surface reflects light is a property called luster. The luster of nonmetallic minerals is described as glassy, silky, waxy, pearly, or earthy.

Another way to identify a mineral is the way it breaks. Some minerals have cleavage, the property of splitting along a smooth, flat surface. Some minerals do not break along flat surfaces, instead they fracture.

Fracture is the property of breaking unevenly or along a curved surface. Hardness is a mineral’s ability to scratch other materials or be scratched by other materials.

A scale on the Moh’s hardness scale ranks minerals from 1 to 10 according to their hardness. Talc is the softest mineral ranked 1 Diamond is the hardest mineral ranked 10 A mineral can scratch another mineral if its hardness value is greater or equal to the other mineral’s hardness value.