Zinnwaldite

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Zinnwaldite
File:Zinnwaldite-172887.jpg
Zinnwaldite from Zinnwald, Germany
General
Category	[[Mineral categories|Mica group]]
Formula	KLiFe2Al(AlSi3)O10(F,OH)2
Strunz classification	[[Strunz classification|]]
Dana classification	[[Dana classification|]]
Crystal system	[[Crystal system|]]
Crystal class
Color	Brown, yellow, green, gray
Physical properties
Cleavage	Perfect on {001}
Mohs scale hardness
Luster	Vitreous, pearly
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity
Optical properties
Refractive index
Crystal habit
Other characteristics

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Zinnwaldite is a mica mineral belonging to the mica group of phyllosilicates. It is a complex lithium-iron aluminium silicate with the chemical formula KLiFe<sub>2</sub>Al(AlSi<sub>3</sub>)O<sub>10</sub>(F,OH)<sub>2</sub>. Zinnwaldite is named after the Zinnwald region in the Ore Mountains on the border between Germany and the Czech Republic, where it was first discovered.

Occurrence

Zinnwaldite is typically found in granite pegmatites and greisens, often associated with other lithium-bearing minerals such as spodumene, lepidolite, and petalite. It is commonly found in regions with significant tin and tungsten mineralization. Notable localities include the Zinnwald region, the Erzgebirge in Germany, and the Czech Republic.

Physical Properties

Zinnwaldite crystallizes in the monoclinic crystal system and forms tabular, pseudohexagonal crystals. It exhibits perfect cleavage on the {001} plane, which is characteristic of micas. The mineral has a Mohs hardness of 3.5 to 4, making it relatively soft. Its specific gravity ranges from 2.9 to 3.2.

The color of zinnwaldite can vary from brown to yellow, green, or gray, and it has a vitreous to pearly luster. It is transparent to translucent and exhibits pleochroism, showing different colors when viewed from different angles.

Chemical Composition

Zinnwaldite is a complex silicate mineral with a layered structure typical of micas. Its chemical composition can be represented as KLiFe<sub>2</sub>Al(AlSi<sub>3</sub>)O<sub>10</sub>(F,OH)<sub>2</sub>. The presence of lithium and iron distinguishes it from other micas such as muscovite and biotite.

Uses

Zinnwaldite is primarily of interest to mineral collectors and researchers studying lithium-bearing minerals. It is not commonly used in industrial applications due to its rarity and the availability of other lithium sources.

See Also

• Mica group
• Lepidolite
• Spodumene
• Petalite
• Greisen