Peridot

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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)

Tags: Bastard emerald, Chrysolite, Dunite, Evening emerald, Fayalite, Forsterite, Hawaiite, Hortonolite, Knebelite, Night Emerald, Olivine Group, Orthorhombic, Peridot