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Formula: CaB2Si2O8
Sorosilicate (Si2O7 groups)
Crystal System: Orthorhombic
Specific gravity: 2.93 to 3.02 measured, 2.99 calculated
Hardness: 7 to 7½
Streak: White
Colour: Colourless, yellowish to dark brown, pink
Solubility: Soluble in acids (Dana)
Common impurities:Fe,Mn,Al,Mg,Sr,Na
Environments:
Plutonic igneous environments
Pegmatites
Metamorphic environments
Hydrothermal environments
Evaporites
Danburite occurs in hypothermal (high temperature) veins, where it is associated with
quartz,
cassiterite,
fluorite and
orthoclase. It occurs in moderate to low temperature and low iron-bearing
contact metamorphic rocks, where it is associated with
andradite,
wollastonite and sulphides.
Other associated minerals include titanite,
axinite, tourmaline,
mica, grossular,
albite, apophyllite,
stilbite,
dolomite,
calcite and gypsum
(HOM)
Danburite occurs in granite and metamorphosed carbonates and
evaporites,
in skarn, in marine
salt deposits and in alpine crevices.
Localities
At Zechstein, Germany, danburite occurs with anhydrite
(Dana).
At the Toroku mine, Takachiho, Nishiusuki District, Miyazaki Prefecture, Japan, danburite is associated with
axinite
(Dana).
Danburite from the Torulo Mine -
Image
At the Anjanabonoina pegmatites, Ambohimanambola, Betafo, Vakinankaratra, Madagascar, the
pegmatite dikes are emplaced in a complex environment of
paragneiss, marble and
orthogneiss, of medium metamorphic grade. Abundant
tourmalinisation extensively affected
schist and quartzite
units. Veins of quartz,
dravite-schorl and danburite
are locally present in metasedimentary rocks close to the
pegmatites
(Mindat).
Danburite from the Anjanabonoina pegmatites -
Image
At Charcas, Charcas Municipality, San Luis Potosí, Mexico,
the primary minerals are
sphalerite, galena,
chalcopyrite, bornite,
tetrahedrite,
arsenopyrite, pyrite and
silver minerals such as jalpaite,
diaphorite and acanthite. In
the host rock, as metamorphic or alteration minerals, danburite,
datolite, hedenbergite,
epidote, chlorite,
andradite, actinolite
and wollastonite have been reported.
Quartz, calcite and
danburite crystallised during the entire life of the systems, throughout
the intrusive emplacement, metamorphism, and mineralising events. With depth, both
sphalerite and galena decrease
while chalcopyrite increases.
Secondary sulphides formed include
bornite, covellite,
digenite and chalcocite.
Native silver, native gold,
hematite and goethite were
deposited after the sulphides
(Minrec 55.6.727-728).
Danburite is ubiquitous in the Charcas camp and has been recorded from every one of the mines. The crystals
are lustrous and opaque to translucent and transparent, in shades of colourless, white, grey, pink and more rarely
pale blue. Some, if not all, specimens fluoresce green under UV. Most danburite crystals are prisms with
chisel-shaped terminations, but some show a more equant habit. They can reach 30 cm in length; crystal groups
weighing more than 100 kg have been collected from cavities over 2 meters in extent. Several finds of pink
danburite have been recorded, and at times, white calcite crystals
have been found attached to the danburite, providing a pleasing colour contrast.
Commonly associated with the danburite are quartz and
calcite and, on occasion,
datolite, scolecite and
millimeter-sized pyrite,
chalcopyrite and
tetrahedrite crystals attached to or included in the
danburite crystals
(Minrec 55.6.727-728).
Quartz
pseudomorphs after danburite have been found
(KL p250).
Danburite from Charcas - Image
At Piz Valatscha, Val Medels, Uri, Graubunden, Switzerland, danburite occurs with
smoky quartz in gneiss
(Dana).
At the type locality, Danbury, Fairfield County, Connecticut, USA, danburite occurs in metamorphosed
limestone
(Dana).
Danburite from Danbury - Image
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