Properties of Minerals

Target #12- I can state how minerals are classified Minerals are classified by their properties Some are easy to study, other require equipment Determined by the chemical composition and crystalline structure Properties Color Streak Luster Cleavage & Fracture Hardness Crystal Shape Density

Target #13- I can explain why color is an unreliable clue to the identify of a mineral Easy to observe with the naked eye Example Quartz Pure: colorless Amethyst: purple (due to the presence of iron and manganese) Sapphire Medium to dark blue in color Caused by the presence of iron and titanium Not generally reliable for identifying a particular mineral Weathered surfaces may hid the color of minerals

Target #14- I can state how you would determine the streak of an unidentified mineral The color of the mineral in a powdered form Easiest way to observe is to rub the mineral against a piece of unglazed tile Different minerals produce different streaks Example Pyrite gold in color, streaks black Minerals harder than the tile will not streak

Target #15- I can describe two types of luster Light that is reflected on a mineral’s surface Either metallic, can reflect light, or non-metallic Non-metallic luster is broken down further Waxy luster Look like candle wax Glassy luster Look like glass Pearly luster Look like pearls Dull luster Lacks any shiny appearance

Target #16- I can contrast cleavage and fracture Cleavage & Fracture Cleavage: the tendency of a mineral to split along specific planes of weakness to form smooth flat surfaces Weaknesses tend to run parallel Example Mica split into sheets Fracture: minerals can break unevenly into pieces that have curved or irregular surfaces Described according to their appearance

Target #17- I can summarize how you would determine the hardness of an unidentified mineral sample The measure of the ability of a mineral to resist scratching Can be determined by using the Mohs hardness scale Scratch an unknown mineral to those found on the hardness scale To test for hardness, you must determine the hardest mineral on the scale that the unknown mineral can scratch If you scratch the unknown with the known, and vice versa, and they do not mark each other, then they are the same hardness

Target #18- I can state how environmental conditions impact mineral formation Crystal Shape Forms into one of six basic shapes Can become more complex as a result of environmental conditions during crystal growth Example Temperature Pressure

Target #19- I can explain the apparent weight differences observed between minerals of the same size Density The ratio of the mass of a substance (how much “stuff” is in it) to the volume of the substance (how much space there is) The more tightly packed the atoms, the more dense a substance is Explains the apparent differences in weight between minerals of the same size