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Properties of Minerals 1. Hardness - resistance to being scratched Mohs Hardness Scale- In 1812, the Austrian mineralogist Friedrich Mohs set a scale of mineral hardness from talc (1) to diamond (10). Any mineral on the scale will only scratch those minerals below it. Field scale- common test using fingernail (1), penny (3), glass (6) 2. Color- not a reliable indicator of identity due to weathering and impurities 3. Streak – leaves a colored powder when rubbed against a hard surface. It’s more reliable than color because streak is not affected by weathering. 4. Density – the amount of matter in a given space, measured in grams/cm3. The ratio of an object’s density to the density of water is called the object’s specific gravity. 5. Luster – how a mineral reflects light on its surface. Minerals can be glassy, metallic, submetallic, or nonmetallic 6. Fracture Cleavage – different minerals have characteristic ways of breaking. Cleavage is the tendency to break along flat surfaces. Ex. Galena and pyrite will always break into a cube.Fracture is the tendency to break unevenly along curved or irregular surfaces. 7. Crystal Shape – the natural growth of a mineral 8. Taste – certain minerals like halite (salt) and sulfur have characteristic flavors 9. Magnetism – Ex. Magnetite has magnetic properties. 10. Reaction to Acid – an acid, such as hydrochloric acid (HCl), can cause a mineral to fizz. 11. Fluorescence – Ex. Calcite and fluorite can glow under UV light. 12. Optical properties – Ex. Calcite can create a double image. * *