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Sinhalite
Current inventory:  1 gem
 

Chemistry:  MgAl(BO₄)

Discovered in 1952;   IMA status: Valid (pre-IMA; Grandfathered).
Sinhalite gets its name is from the old Sanskrit word for Ceylon (now Sri Lanka), sinhala.

Classification

Mineral Classification:

Borates

Strunz 8th Ed. ID:

5/G.07-10

5 : Nitrates, Carbonates & Borates
G : Borates [BO3]3-
07 : Sinhalite - Behierite series

Crystal Data

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

Most occurances are found as rolled pebbles in gem gravels. Rarely found as euhedral crystals, equant to prismatic, to 2 cm; anhedral grains.

Twinning:

None

Physical Properties

Cleavage:

Indistinct

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

6.5 - 7.0

Density:

3.47 - 3.50 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless, pale yellow, yellow, greenish brown, dark brown; brownish pink, pale pink if chromian

Transparency:

Transparent

Luster:

Vitreous (glassy)

Refractive Index:

1.667 - 1.712  Biaxial ( - )

Birefringence:

0.035 - 0.037

Dispersion:

Strong; r > v

Pleochroism:

Weak; X = brown, pale yellow; Y = green, pale brown, bluish gray; Z = paler brown, pale greenish brown, pale pinkish gray

Occurances

Geological Setting:

A rare accessory mineral formed in boron-rich skarns at the contact of limestones with granite or gneiss.

Type Locality:

Sri Lanka

Year Discovered:

1952

View mineral photos:

Sinhalite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Sinhalite is a very rare gem that was long thought to be a brown variety of Peridot but in 1952 an investigation determined it to be a new mineral. It has weak pleochroism from pale brown to yellow to greenish brown. The most notable occurances of Sinhalite are from the gem gravels of Sri Lanka in the Ratnapura district, at Nivitigala, Balangoda, Nirialla; around Elahera and Eheliyagoda; and elsewhere. Also from Mogok, Myanmar, in gem gravels. Non-gem quality material can be found at a few other locations around the world.
 

  
Sinhalite gems for sale: