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Formula: Au2Bi
Alloy of gold and bismuth,
copper group
Crystal System: Isometric
Specific gravity: 15.46 measured, 15.70 calculated
Hardness: 1½ to 2
Colour: Silver white with pink tint, tarnishes to black
Stability: Thermodynamically unstable below ~116°C, but is found in a metastable state in nature (Mindat).
Common impurities: Ag
Environments
Metamorphic environments
Hydrothermal environments
Maldonite occurs in gold - bismuth -
telluride - sulphide assemblages
(AJM 15.25-38).
Localities
At the type locality, Nuggety Reef, Maldon, Mount Alexander Shire, Victoria, Australia, the country rocks hosting the
quartz reefs in the gold field consist of
quartzite and hornfels
with occasional calc-silicate rocks and
skarn. The sequence of mineralisation is within the
biotite - cordierite -
K-feldspar zone of a
contact
aureole surrounding granite.
Assemblages of native bismuth, gold,
maldonite, joséite and
bismuthinite are dominated by
gold and native bismuth; other minerals
found in the assemblages include jonassonite,
aurostibite and hedleyite. The
maldonite occurs as blebs up to 2 mm across surrounded by an irregular
fringe of intergrowths of gold and bismuth
(AJM 15.25-38).
The occurrence is a particularly high-temperature gold -
quartz vein
(Ramdohr p337).
At the Băiţa mining district, Nucet, Bihor County, Romania, maldonite is of high-temperature origin in the
garnetiferous skarn
(Ramdohr p337).
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