Mineralogists use certain properties to identify a mineral: color, luster, hardness, cleavage, and streak. They may also use other tests, including how the mineral reacts to electricity or magnets.

Minerals come in many different colors. They also reflect light in different ways. The luster of a mineral describes how the mineral appears as it reflects light. Some minerals are transparent, or see-through. Others are iridescent, which means that their color changes as light hits them from different directions.

Mineralogists describe a mineral’s hardness with the Mohs scale. The scale lists 10 typical minerals, from the softest (talc) to the hardest (diamond). A mineral can be identified by comparing its hardness to the hardness of these 10 minerals.

The cleavage of a mineral is the way it splits or breaks. Mica, for example, breaks into thin, flat sheets.

Streak is the color of a mineral’s powder. Streak is produced by rubbing a piece of mineral against the surface of rough porcelain, a type of pottery.