Osumilite
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| Osumilite | |
|---|---|
| Category | Mineral |
| Chemical formula | (K,Na)(Fe,Mg)2(Al,Fe)3(Si,Al)12O30·H2O |
| Identification | |
| Color | Rarely transparent to translucent, blue, brown, black, gray |
| Crystal habit | Include prismatic crystals with a pinacoidal termination |
| Crystal system | Hexagonal; 6/m 2/m 2/m. |
| Twinning | Rarely |
| Cleavage | None |
| Fracture | Subconchoidal |
| Mohs Scale hardness | 5 - 6 |
| Luster | Vitreous |
| Optical Properties | Uniaxial (+), w=1.5406, e=1.543, bire=0.0024 |
| Streak | Blue-gray |
| Specific gravity | 2.62 - 2.64 |
| Other Characteristics | Dana class: 63.2.1a.7 |
Osumilite a very rare hydrate potassium-sodium-iron-magnesium-aluminum silicate mineral. Osumilite is part of the of the milarite group (also known as the milarite-osumilite group) of cyclosilicates.
Contents |
[edit] Characteristics
Osumilite chemical formula is (K,Na)(Fe,Mg)2(Al,Fe)3(Si,Al)12O30·H2O. 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.[1]
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.[2]
[edit] Occurrence
Osumilite, 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.[3]
Osumilite is found in the Obsidian Cliffs, Oregon; Sardinia, Italy; Kagoshima and Yamanashi Prefecture, Japan; and the Eifel district in Germany.[3]
[edit] See also
[edit] References
- ^ http://webmineral.com/data/Osumilite-(Mg).shtml Webmineral.com
- ^ http://www.galleries.com/minerals/silicate/osumilit/osumilit.htm Mineral Galleries
- ^ a b http://www.handbookofmineralogy.org/pdfs/osumilite.pdf Handbook of Mineralogy
