Achroite

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Refractive Index : 1.644 – 1.624 (+0.011 – 0.009)

Optical Characteristic : DR U-

Specific Gravity : 3.06 (+0.20 – 0.06)

Formula : Na(Li,Al)3Al6(BO3)3Si6O18(OH)4

Crystal System : Trigonal

Variety/Species : Elbaite

Species/Group : Tourmaline Group

Birefringence : 0.018 to 0 .040

Dispersion : 0.017

Hardness : 7 to 7.5

Toughness : Fair

Ultrasonic : Risky

Steam : Risky

UV Long : Inert

UV Short : Inert

Pleochroism : None

Strength : N/A

Pleochroism Colors : None

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 : N/A

Enhancements : None

Cleavage : None

Color Range : Colorless

Transparency : Transparent to Opaque

Phenomena : None

Separations : Achroite from-
Colorless Topaz: birefringence, optic character, SG, cleavage, spectrum (possibly)Rock Crystal: RI, SG, optic sign
Colorless Sapphire: RI, SG, fluorescence (possibly)Calcite: RI, SG, fluorescence (possibly)

Identifying Characteristics and information
Thread-like liquid and gas inclusions, gas filled fractures.Achroite is a very rare stone.
Birefringence is usually 0.018 – 0.020.

Spectral Data
Not diagnostic.

Trade Names and Misnomers
AchroiteColorless Tourmaline

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