Topic: Identifying Minerals PSSA: 3.5.7.A/S8.D.1.1

Objective: TLW use mineral properties to identify selected unknown minerals.

MI #1: Color and Luster Minerals come in a variety of colors, however, color can change due to impurities and chemical reactions For this reason, color is usually not a reliable identifying characteristic. Luster is the way a mineral shines in reflected light. For our purposes mineral luster will be classified as metallic or non metallic. A more complete reference can be found on p. 70 of your textbook.

MI #2: Streak Streak refers to the color of a mineral in powdered form. Streak is found by rubbing the mineral specimen against a piece of unglazed porcelain called a streak plate. A mineral’s streak is not always the same as its color, and it will not change when exposed to air or water.

MI #3: Cleavage and Fracture Cleavage is the tendency of some minerals to break along smooth, flat surfaces. Fracture is the tendency of some minerals to break along curved or irregular surfaces.

MI #4: Hardness Hardness is a minerals resistance to being scratched. Moh’s hardness scale rates the hardness of a mineral on a scale of 1(softest) to 10 (hardest) and is used to compare hardness. The reference minerals for Moh’s hardness scale are found in Figure 5 on p. 72.

MI #5: Density Density is the ratio of mass to a given volume. It is usually expressed in units of grams/milliliter (g/mL) or grams/centimeter3 (g/cm3). Specific gravity is the ratio of a substances density to the density of water (which is 1 g/mL).

MI #6: Special Properties Some properties are associated with only a few minerals…. Fluorescence – glow in UV light Magnetism – includes magnetite Taste – Do Not Taste the Minerals unless instructed to do so! Double Image – clear calcite shows a double image

So What…? Real Life Application Understanding the properties of minerals allows us to identify minerals.