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Revision as of 04:03, 29 September 2010 by Sncervantes (talk | contribs)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)Annite is a phyllosilicate mineral in the mica family. It has a chemical formula of KFe3AlSi3O10]. Annite is the iron end member of the biotite mica group, the iron rich analogue of magnesium rich phlogopite.
Annite was first described in 1868 for the first noted occurrence in Cape Ann, Rockport, Essex County, Massachusetts, USA and on Pikes Peak, El Paso Co, Colorado. It occurs in igneous and metamorphic rocks that are deficient in magnesium. It occurs associated with fluorite and zircon in the type locality.
| Annite | |
|---|---|
| General | |
| Category | mica group, biotite-phlogopite series. The hydorxl analogue of Flourannite |
| Formula (repeating unit) | KFe3AlSi3O10 |
| Crystal system | monoclinic, pseudohexagonal |
| Identification | |
| Color | reddish brown |
| Crystal habit | usually in "blocks" of thin sheets or as aggregations of foliated thin scales. Includes large, well formed pseudohexagonal prisms up to 12cm across and 15cm long. |
| Twinning | contact twins with composition surface on {001} and twin axis {310} |
| Cleavage | perfect in one direction {001} |
| Fracture | uneven |
| Tenacity | flexible |
| Mohs scale hardness | 2.5 - 3 |
| Luster | submetallic to vitreous; pearly on cleavage surfaces |
| Streak | brownish white |
| Specific gravity | approximately 3.3 g/cm |
| Density | 3.17g |
| Other characteristics | diagnostic: transparent to subopaque; occurrence: in magnesium poor igneous and metamorphic rocks. </references> |
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- ^ Mindat.org
- Deer, W. A., R. A. Howie and J. Zussman, An Introduction to the Rock Forming Minerals, Longman, 1966, p. 212 ISBN 0582442109
- Handbook of Mineralogy
- Hazen, R.M. and C.W. Burnham (1973) The crystal structures of one-layer phlogopite and annite. Amer. Mineral., 58, 889{900.
- Deer, W.A., R.A. Howie, and J. Zussman (1963) Rock-forming minerals, v. 3, sheet silicates, 55{84}.
- Eugster, H.P. and D.R. Wones (1962) Stability relations of the ferruginous biotite, annite. J. Petrol., 3, 82{125.
- Dana, E.S. (1892) Dana's system of mineralogy, (6th edition), 634.
- Kwak, T.A.P. and P.W. Askins (1981) Geology and genesis of the F-Sn-W(-Be-Zn) skarn (wrigglite) at Moina, Tasmania. Econ. Geol., 76, 439{467).