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Formula: PbSiO3
Inosilicate (chain silicate)
Crystal System: Monoclinic
Specific gravity: 6.488 measured, 6.30 calculated
Hardness: 4½
Streak: White
Colour: Colourless to white
Solubility: Gelatinises with acids
Common impurities: Al,Fe,Mn,Ca
Environments
Alamosite is a rare secondary mineral found in the oxidised zone of
lead-bearing deposits
(R&M 96.2.158-163).
Localities
At the San Pascual Mine, Zimapán, Mun. de Zimapán, Hidalgo, Mexico, alamosite is associated with
anglesite, cerussite and
wulfenite
(R&M 96.2.160).
At the type locality, Álamos, Álamos Municipality, Sonora, Mexico, alamosite is associated with
wulfenite, leadhillite and
cerussite
(HOM).
At the Tsumeb mine, Tsumeb, Oshikoto Region, Namibia, alamosite crystals are far superior to those from the type locality. One fine
specimen was found to have a 15 mm crystal of plumbotsumite attached.
Another specimen has been examined in which leadhillite and
anglesite grew on an encrustation of hematite and
mimetite crystals, lining a vug in ore comprising galena,
germanite, tennantite and a little
quartz. Alamosite rested directly on the
mimetite/hematite and clearly predated the
anglesite and leadhillite. Also predating the
anglesite were rare crystals of fleischerite. Both
the anglesite and the leadhillite were spotted with
melanotekite, and flakes of kegelite were found on
some of the anglesite. Alamosite is usually the oldest of the lead silicate minerals here,
but examples of alamosite overgrowing and including melanotekite are also known
(R&M 96.2.158-163).
At the Lucky Cuss Mine, Cochise County, Arizona, USA, alamosite occurs as spherical aggregates of radiating crystals associated
with quartz, queitite and
zeolites
(R&M 96.2.158).
At the Rawhide Mine, Rawhide Wash, Artillery Mountains, Mohave county, Arizona, USA, alamosite is associated with
melanotekite,
shattuckite and wickenburgite
(HOM). Other associates include hyalotekite,
cerussite, chrysocolla,
malachite, mimetite and
wulfenite
(R&M 96.2.159).
At Tiger, Mammoth Mining District, Pinal county, Arizona, USA, alamosite is associated with
diaboleite,
phosgenite, cerussite,
wulfenite and willemite
(HOM).
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