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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 ...
The process of alteration from mafic minerals to serpentine group minerals is called serpentinization. Serpentine minerals are often formed by the hydration of olivine-rich ultramafic rocks at relatively low temperatures (0 to ~600 °C). [15] The chemical reaction turns olivine into serpentine minerals.
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.
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.
Goethite (/ ˈ ɡ ɜːr t aɪ t /, [6] [7] US also / ˈ ɡ oʊ θ aɪ t / [8] [9]) is a mineral of the diaspore group, consisting of iron(III) oxide-hydroxide, specifically the α-polymorph. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient times for its use as a pigment ...
The Kimberley diamonds were originally found in weathered kimberlite, which was colored yellow by limonite, and so was called "yellow ground". Deeper workings encountered less altered rock, serpentinized kimberlite, which miners call "blue ground". Yellow ground kimberlite is easy to break apart and was the first source of diamonds to be mined.
Corundum is a crystalline form of aluminium oxide (Al 2 O 3) typically containing traces of iron, titanium, vanadium, and chromium. [3] [4] It is a rock-forming mineral.It is a naturally transparent material, but can have different colors depending on the presence of transition metal impurities in its crystalline structure. [7]
Igneous rocks rich in magnesium and iron with a color index greater than 90 are defined as ultramafic. [2] Ultramafic rocks may be further classified by their relative proportions of olivine, orthopyroxene, clinopyroxene, and hornblende, which are the most abundant families of mafic minerals in most ultramafic rocks. Peridotite is then defined ...