ClassicGems.net

Danburite

Discovered in 1839; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

CaB₂Si₂O₈

Calcium Boron Silicate

Molecular Weight:

245.86 gm

Composition:

Calcium

16.30 %

Ca

22.81 %

CaO

Silicon

22.85 %

Si

48.88 %

SiO₂

Boron

8.79 %

B

28.32 %

B₂O₃

Oxygen

52.06 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/J.08-20

Nickel-Strunz 10th Ed. ID:

9.FA.65

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H₂O
A : Tektosilicates without additional non-tetrahedral anions

Related to:

Danburite Group. The calcium analogue of Maleevite and Pekovite.

Members of Group:

Danburite Group: Danburite, Maleevite, Pekovite

Varieties:

None

Synonyms:

Bementite (of Dana)

Crystal Data

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

Crystals prismatic, rhomboidal to square in cross section, to 50 cm; also as disseminated masses.

Twinning:

None

Physical Properties

Cleavage:

Indistinct on {001}

Fracture:

Irregular/Uneven to Sub-Conchoidal

Tenacity:

Brittle

Moh's Hardness:

7.0 - 7.5

Density:

2.93 - 3.02 (g/cm³)

Luminescence:

Fluorescent; violet blue under SW UV, blue to blue-green under LW UV. Thermoluminescent (red)

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless, White, wine-Yellow, Yellowish Brown, Greenish; Colorless in thin section.

Transparency:

Transparent to Translucent

Luster:

Vitreous, Greasy

Refractive Index:

1.627 - 1.639  Biaxial ( +/- )

Birefringence:

0.006

Dispersion:

Relatively Strong;  r < v  (0.017)

Pleochroism:

None

Occurances

Geological Setting:

In granite and metamorphosed carbonate rocks associated with hydrothermal activity; in evaporites.

Common Associations:

Titanite, Axinite, Tourmaline, Mica, Quartz, Grossular, Albite, Fluorite, Apophyllite, Stilbite, Datolite, Bakerite, Dolomite, Calcite, Anhydrite, Gypsum

Common Impurities:

Fe, Mn, Al, Mg, Sr, Na

Type Locality:

Danbury, Fairfield County, Connecticut, USA

Year Discovered:

1839

View mineral photos:

Danburite Mineral Photos and Locations

Unusual Gem Categories

Fluorescent Gems, Thermoluminescent Gems

More Information

Mindat.org
Webmineral.com

Danburite is a hard and durable gem that is ideal for jewelry. The dispersion is relatively strong so well cut gems are very bright and attractive. It is not a rare gem except in large sizes. Danburite is usually colorless but also found in several colors including light pink, champagne and yellow to brown.

Danburite was named in 1839 by American mineralogist Charles Upham Shepard (1804 - 1886) for the original discovery location at Danbury, Fairfield County, Connecticut, USA.

Some Danburite specimens may exhibite fluorescence and/or thermoluminescence. Fluorescence is the ability of some minerals to emit visible light when exposured to shortwave (SW) or longwave (LW) ultraviolet (UV) light, or X-rays or electron beams. Thermoluminescence is a property of some minerals to glow when they are heated.

Current sources of gem quality Danburite crystals include colorless to light pink crystals from Charcas, San Luis Potosí, Mexico; colorless to yellow crystals from Mogok, Myanmar (Burma); colorless to yellow crystals from Anjanabonoina and several other locations in Madagascar; and several minor locations in Russia including Bor Quarry, Dal'negorsk, Russia.

Danburite gems for sale: