2.4-2.5 Notes How do we identify minerals? The characteristics of an object that can be observed or measured are its physical properties. Some physical properties of minerals are color, streak, luster, and hardness. Color- Some minerals cannot be identified by color alone, because many minerals are the same color. For example, gold and pyrite are both brassy yellow. Other minerals are found in more than one color. For example, Quartz can be found in many colors, such as pink, purple, yellow, or colorless. Two minerals found only in a single color are malachite (green) and azurite (blue). Streak is the color of the powder left by a mineral. You can find the streak of a mineral by rubbing it across a square unglazed ceramic tile. A mineral can be found in many different colors. However, its streak is ALWAYS the same. Luster refers to the way a mineral’s surface reflects light. Luster is either metallic or non-metallic. Minerals with a metallic luster shine a new coin. Non-metallic lusters are generally referred to as waxy, glassy, or dull. Hardness is the property of a mineral that relates to how much it resists being scratched. The Moh’s scale ranks ten minerals in hardness from 1-10. The higher the number, the harder the mineral. For example, a mineral with a hardness of 10 can scratch any mineral that has a lower number. All matter has mass and volume. Density is the amount of matter in a given volume. The density of a mineral NEVER changes. It is measured in grams per cubic centimeters, or g/cm3 The formula is: Density=Mass/Volume For example, suppose you have a sample of talc that has a mass of 26g and a volume of 10 cm3. If you divide 26g by 10cm3, you will get a density of 2.6 g/cm3. Magnetism is a force of attraction or repulsion shown by matter that is magnetic. Objects made of iron, nickel, cobalt, or steel are attracted to a magnet. Magnetite also shows the property of magnetism. The acid test helps identify minerals that contain calcium carbonate. You place a drop of diluted acid on a small piece of the mineral. If the surface of the mineral fizzes, the mineral contains calcium carbonate.