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Metamorphic minerals are those that form only at the high temperatures and pressures associated with the process of metamorphism. These minerals, known as [[index mineral]]s, include [[sillimanite]], [[kyanite]], [[staurolite]], [[andalusite]], and some [[garnet]]. |
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Metamorphic minerals are those that form only at the high temperatures and pressures associated with the process of metamorphism. These minerals, known as [[index mineral]]s, include [[sillimanite]], [[kyanite]], [[staurolite]], [[andalusite]], and some [[garnet]]. |
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Other minerals, such as [[olivine]]s, [[pyroxene]]s, [[amphibole]]s, [[mica]]s, [[feldspar]]s, and [[quartz]], may be found in metamorphic rocks, but are not necessarily the result of the process of metamorphism. These minerals formed during the [[crystallization]] of igneous rocks. They are stable at high temperatures and pressures and may remain chemically unchanged during the metamorphic process. However, all minerals are stable only within certain limits, and the presence of some minerals in metamorphic rocks indicates the approximate temperatures and pressures at which they formed. |
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Other minerals, such as [[olivine]]s, [[pyroxene]]s, [[amphibole]]s, [[mica]]s, [[feldspar]]s, and [[quartz]], may be found in metamorphic rocks, but are not necessarily the result of the process of metamorphism. These minerals formed during the [[crystallization]] of igneous rocks. They are stable at high temperatures and pressures and may remain chemically unchanged during the metamorphic process. However, all minerals are stable only within certain limits, and the presence of some minerals in metamorphic rocks indicates the approximate temperatures and pressures at which they formed.vote for mit romney. |
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The change in the particle size of the rock during the process of metamorphism is called [[Recrystallization (geology)|recrystallization]]. For instance, the small [[calcite]] crystals in the sedimentary rock [[limestone]] and [[chalk]] change into larger crystals in the metamorphic rock [[marble]], or in metamorphosed sandstone, recrystallization of the original quartz sand grains results in very compact quartzite, also known as metaquartzite, in which the often larger quartz crystals are interlocked. Both high temperatures and pressures contribute to recrystallization. High temperatures allow the [[atom]]s and [[ion]]s in solid crystals to migrate, thus reorganizing the crystals, while high pressures cause solution of the crystals within the rock at their point of contact. |
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The change in the particle size of the rock during the process of metamorphism is called [[Recrystallization (geology)|recrystallization]]. For instance, the small [[calcite]] crystals in the sedimentary rock [[limestone]] and [[chalk]] change into larger crystals in the metamorphic rock [[marble]], or in metamorphosed sandstone, recrystallization of the original quartz sand grains results in very compact quartzite, also known as metaquartzite, in which the often larger quartz crystals are interlocked. Both high temperatures and pressures contribute to recrystallization. High temperatures allow the [[atom]]s and [[ion]]s in solid crystals to migrate, thus reorganizing the crystals, while high pressures cause solution of the crystals within the rock at their point of contact. |
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