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Examining Minerals and Rocks What is a mineral? A mineral is homogenous, naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties. Physical properties citrine rose quartz prasiolite 1. COLOR agate milky quartz amethyst smoky quartz jasper Physical properties The color of a mineral when it is powdered is called the streak of the mineral. Physical properties metallic adamantine glassy The luster of a mineral is the way its surface reflects light. pearly dull waxy Hardness-Mohs scale 1 talc 2 gypsum 3 calcite 4 fluorite 5 apatite 6 feldspar 7 quartz 8…show more content…
mafic rock, with predominance of mafic minerals pyroxenes, olivines and calcic plagioclase; these rocks (example, basalt) are usually dark colored, but not always, and have a higher density than felsic rocks. ultramafic rock, with more than 90% of mafic minerals (e.g., dunite) Sedimentary rocks Sedimentary rocks are classified by the source of their sediments, and are produced by one or more processes that follow: Sedimentary rocks Clastic sedimentary rocks are composed of fragments of older rocks that have been deposited and consolidated boulders greater than 25.6 cm cobbles 6.4 to 25.6 cm pebbles 2 mm to 6.4 cm sand 1/16 mm to 2 mm silt 1/256 mm to 1/16 mm clay less than 1/256 mm Sedimentary rocks Chemical sedimentary rocks form when minerals precipitate from a solution, usually sea water. Halite and gypsum are examples of minerals that precipitate from aqueous solutions to form chemical sedimentary rocks. Biochemical sedimentary rocks are composed of accumulations of organic debris. Coal and some limestones are examples of biological sedimentary rocks. Metamorphic rocks Metamorphic rocks are the result of the transformation of a pre-existing rock type, the protolith, in a process called metamorphism, which means "change in
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