Minerals

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General Information

Tourmaline

Tourmaline is a silicate mineral that originates from Sri Lanka and was shipped to Europe by the V.O.C. for collections and jewellery. 95% of the natural tourmaline consists of schorl, a distinct type of tourmaline. There are also dravite and elbaite as important types.[1]

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Chemical & Physical Information

Trivial NameTourmaline
Chemical NameSilicate
Chemical Formula(Ca,K,Na,-)(Al,Fe,Li,Mg,Mn)3(Al,Cr, Fe,-)6(BO3)3(Si,Al,B)6O18(OH,F)4
Density2,82-3,32 g·cm-3
Molar mass-
Hardness7-7,5
Crytal systemTrigonal
Unit cell?
Crystal habitParallel and elongated, needle-shaped prisms.
FractureUneven, conchoidal and brittle.
CleavageUnclear
ColourBlack, green, purple, pink and brown.
LusterGlass
StreakWhite
OpacitySubtransparent to translucent.
SafetySafe
ExtraSemi-precious.
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Photos

Tourmaline

(1 cm)

Tourmaline

(4 cm)

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Sources

[1] Wikipedia

[2] Specimen from my personal collection, photo taken by me.