Uvite

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Refractive Index : 1.660 – 1.612

Optical Characteristic : DR, Uniaxial negative

Specific Gravity : 3.06 (- 0.20 – 0.06)

Formula : CaMg3(AI5Mg)BSi6O27(OH)3(OH,f)

Crystal System : Trigonal

Variety/Species : Tourmaline

Species/Group : Tourmaline Group

Birefringence : 0.017 to 0.021

Dispersion : 0.017

Hardness : 7 to 7.5

Toughness : Fair

Ultrasonic : Risky

Steam : Risky

UV Long : Inert to weak

UV Short : Inert to weak

Pleochroism : 2 colors

Strength : Weak to strong

Pleochroism Colors : Moderate to strong. Generally light and dark tones of body colors.

Heat : May fracture or change color

Acids : No reaction

Light : Stable

Polish Luster : Vitreous

Fracture : Conchoidal

Fracture Luster : Vitreous

Clarity Type : I to III

Tones : N/A

Saturations : N/A

Cause of Color : Pink-manganese

Enhancements : Heating, Irradiation, acid treatment

Cleavage : None

Color Range : Brown, black, green, blackish brown, brownish black, usuallly dark colored

Transparency : Transparent to opaque

Phenomena : Color change (rare), aventurescence, chatoyancy

Separations : Uvite from-
Natural Topaz : birefringence, optic character, SG, cleavage, spectrum(possibly)Andalusite : Birefringence, optic character, pleochroism, spectrum

Identifying Characteristics and information
thread-like liquid and gas inclusions,gas filled fractures.
Birefringence is usually 0.018 – 0.020 but in dark stones it may be as high as 0.040.

Spectral Data
Not diagnostic. Weak spectra usually observed

Trade Names and Misnomers
Uvite

Tags: Tourmaline, Tourmaline Group, Trigonal