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Zinnwaldite



This article is about the mineral. For the color, see Zinnwaldite (color).
Zinnwaldite

General
CategoryPhyllosilicate mineral
Chemical formulaKLiFeAl(AlSi3)O10(OH,F)2
Identification
ColorLight brown to yellowish- or greenish-white
Crystal habitMicaceous, platey scaly masses, pseudo-hexagonal phenocryst tablets
Crystal systemMonoclinic
TwinningOn composition plane {001}, twin axis [310].
CleavagePerfect basal {001}
FractureUneven
TenacityLaminae flexible, elastic.
Mohs Scale hardness3.5 - 4.0
LusterPearly to vitreous
Refractive indexnα = 1.565 - 1.625 nβ = 1.605 - 1.675 nγ = 1.605 - 1.675
Optical PropertiesBiaxial (-) 2V = 30°
Birefringence0.040 - 0.050
Pleochroismdistinct
StreakWhite
Specific gravity2.9 - 3.1
DiaphaneityTransparent to translucent

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. Commonly associated with topaz, cassiterite, wolframite, lepidolite, spodumene, beryl, tourmaline and fluorite.

It was first described in 1845 in Zinnwald (http://de.wikipedia.org/wiki/Zinnwald), Germany.

References

  • Handbook of Mineralogy
  • Webmineral data
  • Mindat
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Zinnwaldite". A list of authors is available in Wikipedia.
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