Generally colourless, danburite crystals may also be yellow or pink. They form wedge-shaped prisms, much like the ones from colourless topaz but distinguishable by cleavage (poor in danburite, perfect in topaz) and specific gravity (lower in danburite).
First found in the town of Danbury, Connecticut (USA). Gem-quality danburite occurs in Burma, Mexico, Switzerland, Italy and Japan.
Borosilicate of calcium - CaB
Colors / Varieties:
Colorless, white, pink, light to dark yellow, yellowish brown, brown.
Crystal System / Forms:
Orthorhombic System / Prismatic and wedge shaped crystals are common.
Cleavage / Fracture:
None / Uneven Fracture.
; Biaxial positive or negative (depends on wavelengths of light used)
Refractive Index / Birefringence:
1.630 - 1.636 / 0.006
Weak to none.
Crystal inclusions, liquid tubes.
Sky blue to bright blue-green in longwave. Thermo-luminescent: reddish tint when heated. (Phosphoresces)
Sometimes shows line at 580
(didymium lines - rare earth spectrum).
Cause of Color:
Slowly attacked by hydrochloric acid.
Simulants (with separation tests):
, birefringence, inclusions)
In carbonate veins in granite rocks.
Myanmar, Japan, Madagascar, Russia, Mexico.
Cuts & Uses:
Facetted, cabochon, etc.