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Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula K(Mg,Fe) 3 AlSi 3 O 10 (F,OH) 2.It is primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous end-members include siderophyllite and eastonite.
Feldspars, quartz or feldspathoids, olivines, pyroxenes, amphiboles, and micas are all important minerals in the formation of almost all igneous rocks, and they are basic to the classification of these rocks. All other minerals present are regarded as nonessential in almost all igneous rocks and are called accessory minerals.
It is the 63rd most abundant element in the crust. Even though this element is not abundant, it is found in more than 100 mineral species. [20] Antimony is sometimes found natively (e.g. on Antimony Peak), but more frequently it is found in the sulfide stibnite (Sb 2 S 3) which is the predominant ore mineral. [19]
Properties may also be classified with respect to the directionality of their nature. For example, isotropic properties do not change with the direction of observation, and anisotropic properties do have spatial variance. It may be difficult to determine whether a given property is a material property or not.
Cleavage is a physical property traditionally used in mineral identification, both in hand-sized specimen and microscopic examination of rock and mineral studies. As an example, the angles between the prismatic cleavage planes for the pyroxenes (88–92°) and the amphiboles (56–124°) are diagnostic. [1]
Diallage is typically an opaque mineral, but translucent specimens can occur. This mineral forms tabular crystals, meaning the crystals are flatter, and slightly longer than wide. These crystals occur as lamellar masses, meaning the crystals stack on top of each other, and form big chunks. It is a heavy, hard mineral, however, it is fragile.
Lodestone attracting some iron nails Lodestone in the Hall of Gems of the Smithsonian Lodestone attracting small bits of iron. Lodestones are naturally magnetized pieces of the mineral magnetite.
Alabaster windows in the Church of Santa Maria la Mayor of Morella, Spain (built 13th-16th centuries). The English word "alabaster" was borrowed from Old French alabastre, in turn derived from Latin alabaster, and that from Greek ἀλάβαστρος (alábastros) or ἀλάβαστος (alábastos).