a naturally formed, inorganic solid with a crystal structure and a definite chemical composition.

• Synthetic (man-made) materials are not minerals.

• Organic materials produced by plants and animals (such as sugars and proteins) are not minerals.

• Substances with no crystal structure are not minerals. Glass is an example of this.

• The chemical formula of a mineral tells you what’s in it. For example, quartz is made of silicon (Si) and oxygen (O) and has the formula SiO2.

a solid formed by a repeating pattern of atoms.

a measure of how easily a mineral can be scratched.

• Hardness of minerals is measured on a scale of 1 to 10 called Mohs scale.

the way a mineral reflects light

• Examples of luster include metallic, glassy, pearly, dull, waxy, resinous (like pine sap), greasy, chalky, and silky.

the color of a mineral in powdered form.

• Streak is observed by rubbing a mineral on a tile called a streak plate. If a mineral is harder than a streak plate (about 6.5), it will not leave a streak.

a measure of how “light” or “heavy” a material is for its size.

• To find density, divide the mass of the material by its volume.

Density is often measured in grams per milliliter (g/mL).