| 词条 | Osumilite |
| 释义 |
| name = Osumilite | category = Cyclosilicate | boxwidth = | boxbgcolor = | image = Osumilite tablets with Mullite - Ochtendung, Eifel, Germany.jpg | imagesize = 260px | alt = | caption = Osumilite tablets with mullite from Ochtendung, Eifel, Germany. | formula = (K,Na)(Fe,Mg)2(Al,Fe)3(Si,Al)12O30 | dana = 63.02.01a.06 | strunz = 9.CM.05 | system = Hexagonal | class = Dihexagonal dipyramidal (6mmm) H-M symbol: (6/m 2/m 2/m) | symmetry = P6/mcc | unit cell = a = 10.15, c = 14.25 [Å]; Z = 2 | color = Black, dark blue, dark brown, pink, gray | habit = Crystals tabular to prismatic also anhedral and massive | twinning = Rarely | cleavage = None | fracture = Subconchoidal | mohs = 5 - 6 | diaphaneity = Translucent | luster = Vitreous | refractive = w=1.545-1.547, e=1.549-1.551 | opticalprop = Uniaxial (+) anomalously biaxial | birefringence = 0.004 | pleochroism = Strong | streak = Blue-gray | gravity = 2.62 - 2.64 | melt = | fusibility = | diagnostic = | solubility = | references = [1][2][3] }} Osumilite is a very rare potassium-sodium-iron-magnesium-aluminium silicate mineral. Osumilite is part of the milarite group (also known as the milarite-osumilite group) of cyclosilicates. CharacteristicsOsumilite chemical formula is (K,Na)(Fe,Mg)2(Al,Fe)3(Si,Al)12O30.[2][3] It is translucent and the typical coloring is either blue, black, brown, or gray. It displays no cleavage and has a vitreous luster. Osumilite has a hardness between 5-6 on the Mohs hardness scale.[4] The hexagonal crystal structure of osumilite is an unusual molecular make-up. The primary unit is a double ring, with a formula of Si12O30. Normal cyclosilicate have rings composed of six silicate tetrahedrons; Si6O18. In a double ring structure, two normal rings are linked by sharing six oxygens, one from each tetrahedron in each six membered ring.[5] OccurrenceOsumilite, was first discovered as grains in volcanic rocks near Osumi, Japan. It was confused with a similar mineral cordierite because of their similar coloring. It can be found in high-grade metamorphic rocks, xenoliths and in the groundmass of rhyolite and dacite.[6] Osumilite is found in the Obsidian Cliffs, Oregon; Sardinia, Italy; Kagoshima and Yamanashi Prefecture, Japan; and the Eifel district in Germany.[6] Osumulite pseudomorphs are known from a number of ultrahigh-temperature rocks, including those of southern Madagascar See also
References1. ^Mindat.org 2. ^Don S. Goldman, George R. Rossman (1978): The site distribution of iron and anomalous biaxiality in osumilite, In: American Mineralogist, 63, S. 490-498 ((PDF, 961 kB){{dead link|date=March 2018 |bot=InternetArchiveBot |fix-attempted=yes }}) 3. ^E. Olsen, T. E. Bunch (1970): Compositions Of Natural Osumilites, In: The American Mineralogiste, 55, S. 875 - 879 ((PDF, 328 kB)) 4. ^1 Webmineral.com 5. ^http://www.galleries.com/minerals/silicate/osumilit/osumilit.htm Mineral Galleries 6. ^1 2 http://www.handbookofmineralogy.org/pdfs/osumilite.pdf Handbook of Mineralogy 6 : Magnesium minerals|Iron minerals|Potassium minerals|Aluminium minerals|Cyclosilicates|Hexagonal minerals |
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