Danburite Information
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CHEMISTRY CaB2Si2O2
WEARABILITY* Excellent
ENHANCEMENTS None Known
*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!
Text and photos courtesy of Barbara Smigel at Artistic Colored Stones.
CRYSTALLOGRAPHY Orthorhombic
REFRACTIVE INDEX 1.627 - 1.641
HARDNESS 7
SPECIFIC GRAVITY 2.07 - 3.03
CLEAVAGE Indistinct
HEAT SENSITIVE No
SPECIAL CARE INSTRUCTIONS None
For more details see the article on "Hardness and Wearability."
... First discovered in Danbury, Connecticut, this gem has been found and mined in Japan, Mexico, Burma, and Madagascar. It ranges from colorless, to light yellow, or pale pink to tan. With no cleavage, good toughness, and a hardness of seven it makes an excellent jewelry stone that surpasses quartz and rivals topaz in brilliance. Its modest dispersion means that although brilliant, cut gems lack "fire," (spectral color flecks.)
... Interestingly, most specimens fluoresce a sky blue color in long wave UV and phosphoresce red when heated. Due to some heat sensitivity, it is best not to subject this gem to steam cleaning. Otherwise, it requires no special care and can be used in all applications, including rings and bracelets.
... There are no known enhancements, synthetics, or imitations on the market. Joel Arem in his Color Encyclopedia of Gemstones states that although the mineral itself is relatively common, large, facetable pieces are rare. Although it is not common enough to become a major commercial jewelry stone, there is enough material for gem collectors and adventurous jewelry lovers to bring this lovely and under appreciated gem into their collections. Value Factors
... Little has been written as a guide to pricing of this gem. The International Gem Society's Price survey of Internet and standard outlets gives a range of from $20 to about $80 per carat, depending on color and size, but limits itself to small gems.
... Sinkankas and Miller in their Standard Catalog of Gem Values lists wholesale prices as between $100 - $200 per carat for larger stones. In my opinion, this is one of the rare instances of the Sinkankas book being out of sync with the present market. From my experience I would say that $20 to possibly $100 per carat is a more reasonable range for larger pieces.
... In any regard, the tried and true value factors apply to this gem very well. All other things being equal, larger, cleaner, better cut and better colored stones are worth more per carat. The only caveat here, might be that a truly colorless stone would surpass a very pale yellow, or slightly pink stone in per carat value.