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  2. List of rock types - Wikipedia

    en.wikipedia.org/wiki/List_of_rock_types

    Quartzolite – Extremely rare igneous rock made mostly of quartz – An intrusive rock composed mostly of quartz; Rhyodacite – Volcanic rock rich in silica and low in alkali metal oxides – A felsic volcanic rock which is intermediate between a rhyolite and a dacite; Rhyolite – Igneous, volcanic rock, of felsic (silica-rich) composition

  3. Igneous rock - Wikipedia

    en.wikipedia.org/wiki/Igneous_rock

    Igneous rock (igneous from Latin igneus 'fiery'), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust.

  4. List of U.S. state minerals, rocks, stones and gemstones

    en.wikipedia.org/wiki/List_of_U.S._state...

    Leaders of states in the U.S. which have significant mineral deposits often create a state mineral, rock, stone or gemstone to promote interest in their natural resources, history, tourism, etc. Not every state has an official state mineral, rock, stone and/or gemstone, however.

  5. Kimberlite - Wikipedia

    en.wikipedia.org/wiki/Kimberlite

    Kimberlite is an igneous rock and a rare variant of peridotite. It is most commonly known to be the main host matrix for diamonds . It is named after the town of Kimberley in South Africa , where the discovery of an 83.5- carat (16.70 g) diamond called the Star of South Africa in 1869 spawned a diamond rush and led to the excavation of the open ...

  6. Igneous textures - Wikipedia

    en.wikipedia.org/wiki/Igneous_textures

    Phaneritic (phaner = visible) textures are typical of intrusive igneous rocks, these rocks crystallized slowly below Earth's surface. As magma cools slowly the minerals have time to grow and form large crystals. The minerals in a phaneritic igneous rock are sufficiently large to see each individual crystal with the naked eye.

  7. Petoskey stone - Wikipedia

    en.wikipedia.org/wiki/Petoskey_stone

    A Petoskey stone is a rock and a fossil, often pebble-shaped, that is composed of a fossilized rugose coral, Hexagonaria percarinata. [1] Such stones were formed as a result of glaciation, in which sheets of ice plucked stones from the bedrock, grinding off their rough edges and depositing them in the northwestern (and some in the northeastern) portion of Michigan's lower peninsula.