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Formula: Pb2.4Fe3+2Si4O10(CO3)1.7(OH)3).nH2O
Phyllosilicate (sheet silicate)
Crystal system: Monoclinic
Specific gravity: 4.0 measured, 3.89 calculated
Hardness: 2 to 2½
Streak: Greenish yellow to olive-green
Colour: Forest-green to light yellow-green
Luminescence: No fluorescence under long wave or short wave UV
Solubility: Effervesces in cold 1:1 hydrochloric acid, leaving a gelatinous residue
Common impurities: Na,Mg,Ba,Pb
Environments
Metamorphic environments
Hydrothermal environments
Localities
At the type locality, the Shirley Ann group, Big Dodd Spring, Ubehebe Mining District, Cottonwood Mountains,
Panamint Mts, Inyo County, California, USA, the Shirley Ann claim exploits an oxidised
lead deposit in contact metamorphosed and faulted
shaly and silty
limestone. The deposit is notable for an abundance of
copper minerals and scarcity of zinc
minerals relative to the larger mines in the area. The most prominent ore mineral is
cerussite, which replaces galena.
The mineral assemblage includes quartz,
calcite, covellite,
chalcocite, anglesite,
wulfenite, hematite,
limonite, malachite and other
supergene copper
minerals.
Specimens containing ferrisurite were collected at the mine dump. Minerals associated with
ferrisurite include galena,
pyrite, chalcopyrite,
covellite, chalcocite,
quartz, calcite,
hematite, cerussite,
mimetite, wulfenite and
malachite. Ferrisurite probably formed during the early stages
of oxidation as a consequence of the alteration of silicates in close proximity to
galena.
Ferrisurite occurs as compact radial aggregates of fibres embedded in
quartz and cerussite and as
tapering feathery crystals in radiating groups in vugs. Maximum crystal dimensions are 2 mm x 0.01 mm x 0.04 mm.
Individual ferrisurite crystals are transparent to translucent with light yellow-green colour and greenish
yellow streak. Compact radial aggregates have a medium to dark forest green colour and olive green streak
(AM 77.1107-1111).
Ferrisurite from the Shirley Ann group -
Image
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