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Streak plates with pyrite (left) and rhodochrosite (right). The streak of a mineral is the color of the powder produced when it is dragged across an unweathered surface. Unlike the apparent color of a mineral, which for most minerals can vary considerably, the trail of finely ground powder generally has a more consistent characteristic color, and is thus an important diagnostic tool in mineral ...
Associated rock type; With what rock type and/or other minerals is this mineral found? Degree of metamorphism and alteration; Mineral shape, properties or form been altered. Lattice structure and geochemistry; Signature chemical elements and bonds of the mineral. For example, is the mineral hydrous like mica or non hydrous like Jadeite.
Micas (/ ˈ m aɪ k ə z / MY-kəz) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into fragile elastic plates. This characteristic is described as perfect basal cleavage. Mica is common in igneous and metamorphic rock and is occasionally found as small flakes in ...
The other minerals in the rock are termed accessory minerals, and do not greatly affect the bulk composition of the rock. Rocks can also be composed entirely of non-mineral material; coal is a sedimentary rock composed primarily of organically derived carbon. [34] [38]
Staurolite is a regional metamorphic mineral of intermediate to high grade. It occurs with almandine garnet, micas, kyanite; as well as albite, biotite, and sillimanite in gneiss and schist of regional metamorphic rocks. [7] It is the official state mineral of the U.S. state of Georgia and is also to be found in the Lepontine Alps in Switzerland.
Rhodochrosite is a manganese carbonate mineral with chemical composition MnCO 3. In its pure form (rare), it is typically a rose-red colour, [5] but it can also be shades of pink to pale brown. It streaks white, [6] and its Mohs hardness varies between 3.5 and 4.5. Its specific gravity is between 3.45 and 3.6. [7]
Feldspars crystallize from magma as both intrusive and extrusive igneous rocks [7] and are also present in many types of metamorphic rock. [8] Rock formed almost entirely of calcic plagioclase feldspar is known as anorthosite. [9] Feldspars are also found in many types of sedimentary rocks. [10]
Serpentine subgroup is a set of common rock-forming hydrous magnesium iron phyllosilicate ((Mg,Fe) 3 Si 2 O 5 4) minerals, resulting from the metamorphism of the minerals that are contained in mafic to ultramafic rocks. [6] They may contain minor amounts of other elements including chromium, manganese, cobalt or nickel.