Montebrasite

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Montebrasite is a light green to yellow or colorless gemstone that belongs to the amblygonite group. Similar to amblygonite in chemical composition, it has less fluorine content and twinned crystals are common. Montebrasite was named for its discovery in Montebras, France.

Montebrasite Polished
Montebrasite Classification
Common Name Montebrasite
Species Montebrasite
Montebrasite Optical Properties
Transparency Transparent
Refractive Index 1.594-1.633
Birefringence 0.02-0.022
Optic Character Biaxial
Optic Sign Positive
Polariscope Reaction Doubly Refractive (DR)
Fluorescence SWUV: Inert
LWUV: Inert to weak green
Pleochroism Unobservable
Montebrasite Characteristic Physical Properties
Hardness 5.5-6
Streak White
Specific Gravity 2.980-3.110
Toughness Poor
Luster Vitreous
Fracture Uneven, Subconchoidal
Cleavage Perfect, in one direction, Good, in two directions
Montebrasite Chemistry & Crystallography
Chemical Name lithium sodium aluminum phosphate
Chemical Formula LiAl(PO4)(OH,F)
Crystal System Trigonal
Chemistry Classification Phosphate

Montebrasite Colors

  • Gray Montebrasite Gray

Countries of Origin

Brazil

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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.