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.
Quartz is one of the most common minerals in the Earth's crust. It is made of silicon dioxide (SiO2), otherwise known as silica. Varieties of quartz based on color include: amethyst, smoky quartz, rose quartz, and citrine. Quartz has a glassy luster and a hardness of 7.