Forsterite

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Forsterite is a colorless to greenish transparent member of the olivine mineral family, which also includes peridot. Forsterite has a heavy magnesium chemical composition and large crystals are not common, but highly sought after by collectors.

Forsterite Polished
Forsterite Classification
Common Name Forsterite
Species Olivine
Forsterite Optical Properties
Transparency Transparent - Translucent
Dispersion Strength: None
Refractive Index 1.635-1.671
Birefringence 0.034-0.035
Optic Character Biaxial
Optic Sign Positive
Polariscope Reaction Doubly Refractive (DR)
Fluorescence SWUV: Inert to weak greenish yellow
LWUV: Inert to weak orangy white
Pleochroism Dichroic, unobservable or weak, varying shades of body color
Forsterite Characteristic Physical Properties
Hardness 6.5-7
Streak White
Specific Gravity 3.230-3.260 Typical:3.200
Toughness Poor
Luster Vitreous
Fracture Conchoidal
Cleavage Good, in two directions
Forsterite Chemistry & Crystallography
Chemical Name magnesium silicate
Chemical Formula Mg2SiO4
Crystal System Orthorhombic
Chemistry Classification Silicate

Alternate Names

Synthetic Forsterite, Tanzanite Simulant

Countries of Origin

Tajikistan

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Creation Classification

Lab Created

Synthetic forsterite (a variety of olivine) is produced by a process called the Czochralski method.Material containing the elements that make up the mineral forsterite (magnesium, silicon, and oxygen) are melted in a platinum crucible.A small forsterite crystal (called a seed) that is attached to a rod is then dipped into the melt and slowly pulled away as the crystal grows around the seed.For this reason, the Czochralski method is also known as crystal pulling.Synthetic gems have the same chemical, optical, and physical properties of their natural counterparts, but are a more cost-effective alternative to a natural gem.

Lab Created Forsterite
Lab Created Classification
Common Name Lab Created
Lab Created Optical Properties
Refractive Index 1.635-1.67
Fluorescence SWUV: Weak greenish yellow
LWUV: Weak chalky orangy yellow
Pleochroism Dichroic, strong blue and purplish pink
Lab Created Characteristic Physical properties
Specific Gravity 3.23
Inclusions Synthetic forsterite sometimes includes gas bubbles, tiny white specks, minute needles
Tim Matthews

Author

Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.