Collectible minerals - full range in stock "Tourmaline"

Tourmaline is a group of boron-containing minerals of variable composition similar in composition. It has the following types and subspecies:

      Elbaite, Na(Al,Li)3Al6(BO3)3[Si6O18](O,OH,F)4, including
        Rubellite - pink to red
        Indicolite - sapphire blue
        Verdelite - green
        Achroite - colorless
      Dravite, NaMg3Al6(BO3)3[Si6O18](O,OH,F)4 , including Uvit CaMg3Al6
      Schorl, NaFe3Al6(BO3)3[Si6O18](O,OH,F)4

They have the property of hemimorphism - asymmetric faceting of the sides of different ends of the crystal. A well-faceted end becomes negatively charged when heated, while the other, less well-cut end is positively charged. Large crystals of tourmaline are used in radio engineering. Tourmalines are widely used in jewelry and in collecting.

You can see tourmaline stone for sale and buy it in the Minerals of Russia online store.

Physical properties of Tourmaline

General
Category	Cyclosilicate
Formula (repeating unit)	(Ca,K,Na,▢)(Al,Fe,Li,Mg,Mn)₃(Al,Cr, Fe,V)₆(BO₃)₃(Si,Al,B)₆O₁₈(OH,F)₄
IMA symbol	Tur
Crystal system	Trigonal
Crystal class	Ditrigonal pyramidal (3m) H-M symbol: (3m)
Space group	R3m (no. 160)
Identification
Color	Most commonly black, but can range from colorless to brown, red, orange, yellow, green, blue, violet, pink, or hues in between; can be bi-colored, or even tri-colored; rarely can be neon green or electric blue
Crystal habit	Parallel and elongated. Acicular prisms, sometimes radiating. Massive. Scattered grains (in granite).
Cleavage	Indistinct
Fracture	Uneven, small conchoidal, brittle
Tenacity	Brittle
Mohs scale hardness	7.0–7.5
Luster	Vitreous, sometimes resinous
Streak	White
Diaphaneity	Translucent to opaque
Specific gravity	3.06+0.20−0.06
Density	2.82–3.32
Polish luster	Vitreous
Optical properties	Double refractive, uniaxial negative
Refractive index	n_ω = 1.635–1.675 n_ε = 1.610–1.650
Birefringence	−0.018 to −0.040; typically about −0.020 but in dark stones it may reach −0.040
Pleochroism	Typically moderate to strong Red: definite; dark red, light red Green: strong; dark green, yellow-green Brown: definite; dark brown, light brown Blue: strong; dark blue, light blue
Dispersion	0.017
Ultraviolet fluorescence	Pink stones; inert to very weak red to violet in long and short wave
Absorption spectra	Strong narrow band at 498 nm, and almost complete absorption of red down to 640 nm in blue and green stones; red and pink stones show lines at 458 and 451 nm as well as a broad band in the green spectrum

archived

Code: 2652

Tourmaline 2-head

Malkhan, stone vein "October", Transbaikalia, Eastern Siberia, RF

32*12*5mm

0.00 $ $59.00

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