List of Gemstones | Rare Minerals | Gem stones | Gems » Forsterite http://www.all-gemstones.com www.all-gemstones.com    Thu, 06 May 2010 12:29:47 +0000 http://wordpress.org/?v=2.8.6 en hourly 1 Peridot http://www.all-gemstones.com/peridot http://www.all-gemstones.com/peridot#comments Wed, 12 Aug 2009 10:32:10 +0000 admin http://www.all-gemstones.com/?p=1121
Refractive Index : 1.690 – 1.654 (+0.020 – 0.020)
Optical Characteristic : DR, biaxial positive or negative
Specific Gravity : 3.34 (+0.14 – 0.07)
Formula : Mg2SiO4-Fe2SiO4
Crystal System : Orthorhombic
Variety/Species : Peridot
Species/Group : Olivine group
Birefringence : 0.035 to 0.038
Dispersion : 0.020
Hardness : 6.5 to 7
Toughness : Fair to good
Ultrasonic : Risky
Steam : Never
UV Long : Inert
UV Short : Inert
Pleochroism : 2 colors
Strength : Weak to moderate
Pleochroism Colors : Weak yellow green and green, noticeable only in dark stones
Heat : Avoid abrupt temperature change
Acids : Avoid pickling acid
Light : Stable
Polish Luster : Vitreous
Fracture : Conchoidal
Fracture Luster : Vitreous to subvitreous
Clarity Type : ll
Tones : 2-7
Saturations : 1-4
Cause of Color : Iron
Enhancements : None
Cleavage : Imperfect to weak.
Color Range : yellowish green , greenish yellow to brownish green
Transparency : Transparent to translucent (in highly included stones)
Phenomena : Asterism (extremely rare), aventurescence
Separations : Nartural Peridot from-Diopside : RI, birefringence, optic sign (beta position), spectrumSpodumene : RI,SG, birefringence, spectrum, fluorescence

Tourmaline : RI, SG, birefringence, optic character, pleochroism, spectra

Dioptase : Appearance, birefringence, optic character, spectrum, cleavage

Zoisite : Color, birefringence, pleochroism, spectrum

Synthetic spinel triplet: RI, immersion, magnification, SG
Identifying Characteristics and information
Moderate doubling,”lily pad” liquid and gas inclusions, octahedral chromite inclusions (dark). Peridot belongs to the Forsterite-Fayalite mineral series (part of the olivine Group). There is more magnesium (Mg) than iron (Fe) in the finer qualities of peridot.
Spectral Data
3 main bands: strong at 4930, narrow at 4730 and broad at 4530. Vague bands at 6530 and 5290.
Trade Names and Misnomers
Bastard emerald (M)
Chrysolite
Dunite
Evening emerald (M)
Fayalite
Forsterite
Hawaiite
Hortonolite
Knebelite
Night Emerald (M)
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