Zinnwaldite
| Zinnwaldite | |
|---|---|
 | |
| General | |
| Category | Phyllosilicate mineral |
| Formula (repeating unit) | KLiFeAl(AlSi3)O10(OH,F)2 |
| Crystal system | Monoclinic |
| Identification | |
| Color | Light brown to yellowish- or greenish-white |
| Crystal habit | Micaceous, platey scaly masses, pseudo-hexagonal phenocryst tablets |
| Twinning | On composition plane {001}, twin axis [310]. |
| Cleavage | Perfect basal {001} |
| Fracture | Uneven |
| Tenacity | Laminae flexible, elastic. |
| Mohs scale hardness | 3.5 - 4.0 |
| Luster | Pearly to vitreous |
| Streak | White |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 2.9 - 3.1 |
| Optical properties | Biaxial (-) 2V = 30° |
| Refractive index | nα = 1.565 - 1.625 nβ = 1.605 - 1.675 nγ = 1.605 - 1.675 |
| Birefringence | 0.040 - 0.050 |
| Pleochroism | distinct |
| References | [1][2][3] |
Zinnwaldite, KLiFeAl(AlSi3)O10(OH,F)2, is a potassium lithium iron aluminium silicate hydroxide fluoride silicate mineral in the mica group.
It occurs in greisens, pegmatite, and quartz veins often associated with tin ore deposits. It is commonly associated with topaz, cassiterite, wolframite, lepidolite, spodumene, beryl, tourmaline, and fluorite.
It was first described in 1845 in Zinnwald/Cinovec on the German-Czech Republic border.
References
- ^ http://rruff.geo.arizona.edu/doclib/hom/zinnwaldite.pdf Handbook of Mineralogy
- ^ http://webmineral.com/data/Zinnwaldite.shtml Webmineral data
- ^ http://mindat.org/min-4419.html Mindat
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