Danburite

Danburite is a borosilicate mineral named after the location where it was first discovered - Danbury, in Connecticut, USA. It was first found in 1839 by one Charles Upham Shephard. Danburite has the chemical formula Its chemical formula is CaB2(SiO4)2.[1]

Danburite
(From Sri Lanka or Madagascar (?). Weight: 3.51 carats)
Image © supplied by Woodmansee* Gems

Danburite comes in colors ranging from light pink to yellow. It is very hard (7-7.5 Mohs) and quite durable. It has a refractive index of around 1.63 and also has good dispersion - for these reasons it is quite popularly used as a diamond imitation in jewelry. Large crystals of Danburite above 45 carats are rare.

Danburite - Occurrence

Danburite is not particularly rare. The crystals are found in a number of localities around the world, including in Australia, Bolivia, Canada and Russia. It can occur in a number of "pastel" colors. The colorless crystals of Danburite are found most commonly in Danbury in Connecticut, USA and in some localities in Mexico. The light pinkish colored crystals of Danburite have also been found in the localities of Mexico in San Luis Potosi. The yellow colored crystals of Danburite have largely been mined in Burma. The localities in Burma have also produced large quantities of colorless crystals of Danburite.

Similarly the colorless crystals of Danburite and the yellow colored crystals of Danburite are found in Madagascar. Several locations in Russia have yielded the extremely rare light brown colored crystals of Danburite. The largest gemstones of Danburite have been found in Mexico which weigh over 50 carats. These gemstones of Danburite are exceptionally clear and quite bright and sparkly thus commanding high prices in the niche gemstone markets.

Danburite Properties:

Danburite is composed of calcium boron silicate and has a molecular weight of approx. 245 grams. Danburite is composed of 16 percent calcium, 23 percent silicon and 52 percent oxygen. The dominant silicon in Danburite classify it as a silicate mineral.

Emerald Cut Danburite
Weight: 7 carats. From Brazil.

Danburite displays orthorhombic and dipyramidal crystallography and in its natural form is often found as large crystal masses measuring at least 50 cm in size. The cleavages on the Danburite crystals are indistinct with irregular and often uneven fracturing. The Danburite crystals also sometimes display sub-conchoidal fracturing. Danburite crystals are quite brittle and display luminescence properties.

Danburite occurs in colorless form as well as in the colors of light pink, aqua blue, light yellow and light brown. Extremely rarely, gemstones of Danburite are found with a greenish hue. The gemstones of Danburite range in clarity from transparent to translucent. Gem quality Danburite has the pleasing quality of being relatively free from inclusion and the gemstones are usually very clear and bright to the eye.

The luster of Danburite crystals ranges from vitreous to greasy and the dispersion of the crystals is quite strong. Danburite crystals are naturally found in evaporites and in metamorphosed rocks with high hydrothermal activity. The largest and brightest Danburite gemstones are prized possessions - and for the best stones over 10 carats, prices may well be over $50 per carat. However smaller stones may be obtained for only a few dollars per carat.

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Danburite - Sources Referenced:

[1]

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