Typical physical properties of Tourmaline powder

Author:未知　Date:2014年01月24日　Source:互联网 Views:

Core tips: Density 2.82-3.32 Hardness

Density	2.82-3.32
Hardness	7-7.5
Crystal habit	Parallel and elongated. Acicular prisms, sometimes radiating. Massive. Scattered grains (in granite)
Crystal system	Trigonal
Cleavage	Indistinct
Fracture	Uneven, small conchoidal, brittle
Luster	Vitreous, sometimes resinous
Streak	White
Specific gravity	3.06 (+.20 -.06)
Polish luster	Vitreous
Optical properties	Double refractive, uniaxial negative
Refractive index	nω=1.635–1.675, nε=1.610–1.650
Birefringence	-0.018 to -0.040; typically about .020 but in dark stones it may reach .040
Pleochroism	typically moderate to strong Red Tourmaline: Definite; dark red,light red Green Tourmaline: Strong; dark green, yellow-green Brown Tourmaline: Definite; dark brown, light brown Blue Tourmaline: Strong; dark blue, light blue
Dispersion	.017
Ultraviolet	pink stones—inert to very weak
Fluorescence	red to violet in long and short wave
Absorption spectra	a strong narrow band at 498 nm, and almost complete absorption of red down to 640nm in blue and green stones; red and pink stones show lines at 458 and 451nm as well as a broad band in the green spectrum