andradite Member of the garnet group of minerals, Ca3Fe2(SiO4)3; sp. gr. 3.75; hardness 6.5–7.5; cubic; yellow, greenish, or brownish-red, to black; greasy to vitreous lustre; most crystals dodecahedral; occurs widely in metamorphic and igneous rocks often as a result of metasomatism, also in beach sands and alluvial placers. Transparent crystals are used as gemstones, and the mineral can be used as an abrasive.
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Almandine , almandine Member of the garnet group of minerals, Fe3Al2(SiO4)3; sp. gr. 4.25; hardness 6.5–7.5; cubic; red, brown-red, or black; greasy to vitreous… wolframite , wolframite Ore mineral for tungsten, with the formula (Fe,Mn)WO4; sp. gr. 7.0–7.5; hardness 5.0–5.5; monoclinic; grey-black to brownish-black; browni… Cancrinites , haüyne A feldspathoid and member of the sodalite group of minerals, formula (Na,Ca)4–8(Al6Si6O24)(SO4,S)1–2; sp. gr. 2.5; hardness 5.5; greyish-white… chromite , chromite Member of the chromite group of minerals in the spinel group, Fe2+Cr2O4, along with magnesiochromite (MgCr2O4); sp. gr. 5.1; black; sub-meta… ilmenite , ilmenite Mineral, FeTiO3; sp. gr. 4.5–5.0; hardness 5–6; trigonal; black; black to brownish-red streak; sub-metallic lustre; crystals normally thick… Biotite , biotite biotite An important rock-forming silicate mineral; a member of the mica group K2(Mg,Fe)6[Si3AlO10]2(OH,F)4, in which the Mg/Fe ratio is less…
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