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A colorless or yellow transparent crystal occasionally used as a Gemstone. Danburite is composed of calcium borosilicate. It was named for its first reported occurrence in Danbury, Connecticut. Colorless danburite is mined in Japan and Mexico (San Luis Potosi) and yellow danburite is mined in Madagascar and Myanmar.


Danburite IR-ATR RRUFF R040013.png

Raman (RRUFF)

Danburite Raman RRUFF R040013.png

Raman (RASMIN)


Synonyms and Related Terms

calcium borosilicate

Physical and Chemical Properties

  • Orthorhombic system with prismatic crystals
  • Poor cleavage in one direction
  • Fracture = uneven to subconchoidal
  • Luster = vitreous to greasy
  • Streak = colorless to white
  • Fluorescence = inert or strong light blue to blue-green (LW); inert or weaker violet blue (SW); red thermoluminescence
  • Pleochroism = none
Composition CaB2Si2O8
Mohs Hardness 7.0 - 7.5
Density 2.93 - 3.02 g/ml
Refractive index 1.630 - 1.636
Birefringence 0.006

Resources and Citations

  • Gem Identification Lab Manual, Gemological Institute of America, 2016.
  • Mineralogy Database: Danburite
  • R.F.Symmes, T.T.Harding, Paul Taylor, Rocks, Fossils and Gems, DK Publishing, Inc., New York City, 1997
  • C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979
  • Wikipedia: Danburite (Accessed Sept. 7, 2005 and Dec 2022)

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