Topaz

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Refractive Index : 1.627-1.619 (+ 0.010 – 0.010)

Optical Characteristic : DR, Biaxial positive

Specific Gravity : 3.53 (+ 0.04 – 0.04)

Formula : AI2(F,OH)2SiO4

Crystal System : Orthorhombic

Variety/Species : All

Species/Group : Topaz

Birefringence : 0.008 to 0.010

Dispersion : 0.014

Hardness : 8

Toughness : Poor

Ultrasonic : Never

Steam : Never

UV : Yellow to brown, pink to red : weak to moderate orange-yellow (LW), gnerally weaker in SW,

Some pinks : Moderate greenish white (SW)

Blue, colorless : Inert to weak yellow or green (LW), generally weaker in SW

UV Short : See above

Pleochroism : 2 or 3 colors

Strength : Weak to moderate

Pleochroism Colors : Yellow : Weak to moderate brownish yellow, yellow and orange-yellowBrown : Weak to moderate yellow brown and brownRed and pink : Weak to moderate light red and orangy red to yellow

Green : Weak to moderate brownish blue-green and light green

Blue : Weak to moderate different tones of blue

Heat : May fracture

Acids : Slightly attacked by acids

Light : some may fade

Polish Luster : Vitreous

Fracture : Conchoidal

Fracture Luster : Vitreous

Clarity Type : I

Tones : 2-8

Saturations : 1-5

Cause of Color : Pink, red – chromium;Blue, yellow and brown – various color centersOthers – color centers and chromium.

Enhancements : Heating, irrradiation

Cleavage : Perfect basal in 1 direction

Color Range : Colorless. yellow, brown, pink, red, purble-red, red-purple, orange, green, yellowish green, greenish yellow, purplish, yellow-brown, blue, pale blue, medium blue

Transparency : Transparent

Phenomena : Chatoyancy (rare)

Separations : Natural Topaz from-

Tourmaline : Birefringence, optic character/sign, SG, cleavage

Andalusite : SG, pleochroism, cleavage, color

Beryl : RI, SG, optic character/sign, cleavage

Quartz : RI, SG, optic character, cleavage, spectrum

Synthetic spinel : RI, optic character, cleavage

Apatite : SG, optic character/sign, birefringence, cleavage, spectrum

Danburite : SG, Birefringence, cleavage

Identifying Characteristics and information
2 or 3-phase inclusions. Faint doubling of facet edges visible in the microscope. Cream phosphorescene(rerely)
May show only 2 colors of pleochrosim

Spectral Data
Not diagonistic.

Trade Names and Misnomers
Blue topaz(S)
Cat’s Eye Topaz(S)
Colorless Topaz
Finder’s Diamond(M)
Hyacinth Topaz
Imperial Topaz(S)
Killiecrankie Diamond(M)
Mogok Diamond(M)
Precious Topaz
pycnite

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Topaz