Topaz : birefringence, optic character, SG, cleavage, spectrum(possibly)

Andalusite : birefrigence, optic character, pleochrosim, SG

Peridot : RI, SG, birefringence, optic character, pleochrosim, spectrum

Iolite : RI, SG, optic character, pleochroism Identifying Characteristics and information

Thread-like liqiud 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 ]]> http://www.all-gemstones.com/tourmaline-group/feed 0 http://www.all-gemstones.com/watermelon-tourmaline http://www.all-gemstones.com/watermelon-tourmaline#comments Fri, 25 Dec 2009 04:43:29 +0000 admin http://www.all-gemstones.com/?p=1486

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,AI)3AI6(BO3)3Si6018(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 to weak

UV Short : Inert to weak

Pleochroism : 2 colors

Strength : Weak to strong

Pleochroism Colors : Green tones or Green/brown

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 : 2-8

Saturations : 1-5

Cause of Color : Green-iron, chromium, vanadium; pink-maganese

Enhancements : Heating, Irradiation, acid treatment

Cleavage : None

Color Range : Pink and green, gren and pink, particolor, multicolor. Pink in the center with a “rind”of green similar to watermelon.

Transparency : Transparent to Opaque

Phenomena : Color change, (rare), aventurescence, chatoyancy

Separations : Watermelon Tourmaline from- Unique appearance

Identifying Characteristics and information Thread-like liquid and gas inclusions,gas filled fractures. Birefringence is usually0.018 – 0.020 Pink in the center with a “rind”of green simillar to watermelon.

Spectral Data Not diagnostic. Weak spectra usually observed

Trade Names and Misnomers Watermelon Tourmaline

]]> http://www.all-gemstones.com/watermelon-tourmaline/feed 0 http://www.all-gemstones.com/uvite http://www.all-gemstones.com/uvite#comments Tue, 18 Aug 2009 06:15:28 +0000 admin http://www.all-gemstones.com/?p=1450   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