Many minerals are coveted around the world for their striking beauty, rarity, and gem quality. But what is a mineral?

A mineral is a solid, naturally occurring, inorganic substance that generally forms crystals. They are the building blocks of rocks and are described based on their physical properties which include: luster, cleavage, streak, hardness, color, and specific gravity.

• Cleavage: The tendency of a mineral to break along weak planes.
• Color: Most minerals have a distinctive color while others are variable in color.
• Hardness: A measure of a mineral's resistance to scratching. This is measured by scratching it against another substance of known hardness on the Mohs Hardness Scale.
• Luster:The reflection of light from the surface of a mineral, described by its quality and intensity. Luster is described as metallic, glassy, dull, earthy, etc.
• Nonsilicate minerals: A mineral without silicon (Si).
• Silicate: Refers to the chemical unit silicon tetroxide, SiO4, the fundamental building block of silicate minerals. Silicate minerals make up most rocks we see at the Earth's surface.
• Streak: Streak refers to the color of the residue left by scratching a mineral on a tile of unglazed porcelain.

Common Minerals