Mineral 1.0: Tourmaline

Mineral 1.0

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Tourmaline with Lepidolite (c) Mineral Picture courtesy of www.yuprocks.com
Tourmaline with Lepidolite
Mineral Picture courtesy of www.yuprocks.com

TourmalineNa(Mg,Fe,Li,Mn,Al)₃Al₆(BO₃)₃Si₆O₁₈(OH,F)₄

Class: Silicate
Subclass: Cyclosilicate
Hardness: 7 - 7.5
Density: 3.0 - 3.2
Streak: White to gray
Lustre: Vitreous, shining-pearly
Habit: Prismatic crystals, very striated faces
Colours: Black, any colour
   Crystal System: Hexagonal
Cleavage: Very indistinct
Fracture: Conchoidal
Magnetism: None
Reaction with HCl: None
Identification in hand sample:
Columnar crystals and vertical striations are characteristic, also has poor cleavage.
Associations:
Typical in granitic pegmatites, accessory in granite, granodiorite and related felsic igneous rocks. Also in schist, gneiss, quartzite and phyllite.
Industrial / ecomonic uses:
Gemstone. Due to piezoelectric properties, it is also used in the manufacture of pressure gauges and other electronic components.
Comments:
Can be a multitude of different colours, depending on the variety.



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