Minerals

Three Types of Rocks

According to the composition, rocks can be divided into igneous rocks (magmatic rocks), sedimentary rocks and metamorphic rocks. In the whole crust, the igneous rock is about 95%, the sedimentary rock is less than 5%, and the metamorphic rock is the least. However, the distribution of the three kinds of rocks varies greatly in different …

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Gabbro

  Gabbro is an igneous rock that has crystallized deep in the Earth. Since the rock cooled and hardened (and crystallized) deep below the Earth’s surface, it will be coarse-grained. High pressure is usually found deep below the surface of the Earth. Here, molten material cools very slowly. The igneous rocks produced have large crystals. …

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Iron

  Iron (element #26, symbol Fe) is the most common metallic element in the universe.  When pure it is a dark, silvery-gray metal. It is a very reactive element and oxidizes (rusts) very easily. Type:  Element (Minerals/Ores of) Color: Metallic gray, dull to bright red (hematite), black, gray with brownish tint in the reflected sun …

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Sandstone

  Sandstone is a sedimentary rock composed mostly of quartz sand, but it can also contain significant amounts of feldspar, and sometimes silt and clay. Sandstone that contains more than 90% quartz is called quartzose sandstone. When the sandstone contains more than 25% feldspar, it is called arkose or arkosic sandstone. Type:  Rock Color: Light …

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Quartzite

  Quartzite is a metamorphic rock derived from sandstone that is distinguished from sandstone by its fracture. Sandstone breaks along grain boundaries, whereas rock is so well indurated (hardened) that it breaks across constituent grains.  Type:  Rock Color: Usually white or gray, can be other colors, due to impurities.   Description Quartzite is a metamorphic …

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Kaolinite

  Kaolinite is a layered silicate clay mineral that forms from the chemical weathering of feldspar or other aluminum silicate minerals. It is usually white, with occasionally a red color impurity due to iron oxide, or blue or brown from other minerals.  Type:  Mineral Color: White, sometimes red, blue or brown tints from impurities   …

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Granite

  Granite is the most widespread of igneous rocks, underlying much of the continental crust. Granite is intrusive igneous rock. Intrusive rocks form from molten material (magma) that flows and solidifies underground, where magma cools slowly.  Type:  Rock Color: light grey or light white   Description Granite is the most widespread of igneous rocks, underlying …

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