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Formula: Pb2Si4O10.H2O
Hydrated phyllosilicate (sheet silicate)
Crystal system: Orthorhombic
Specific gravity: 3.96 measured, 3.940 calculated for the empirical formula
Hardness: 5
Streak: White
Colour: Pale blue to very light blue-green
Luminescence: No fluorescence under UV
Solubility: Decomposes immediately (and dramatically) in cold, dilute hydrochloric acid with exfoliation and
formation of a white precipitate of PbCl2 (cotunnite)
(HOM).
Environments
Sedimentary environments
Metamorphic environments
Localities
At the type locality, the Blue Bell Mine, Zzyzx, Soda Mountains, Silver Lake Mining District, San Bernardino
County, California, USA, as early as 1949, rich specimens of linarite,
caledonite and leadhillite
were known from the deposit. Collecting efforts have continued to yield unusual oxidation-zone assemblages of rare
minerals; Some of the more significant recent (in 2009) discoveries have been
kuksite, quetzalcoatlite
and plumbotsumite.
Plumbophyllite is found in cracks and narrow veins in a highly siliceous
quartzite-like
hornfels in a fractured and chaotic region of
limestone showing irregular
skarn formation. These cracks appear to have been initially filled
largely with cerussite, silica, and/or
chrysocolla.
The plumbophyllite appears to be a tertiary mineral formed from the
cerussite. Species observed in direct association with
plumbophyllite include cerussite,
chrysocolla, fluorite,
goethite, gypsum,
mimetite, opal,
plumbotsumite,
pyromorphite, quartz,
sepiolite and wulfenite.
Other species identified nearby include fluorapatite,
beudantite, boleite,
calcite, celestine,
creaseyite, dioptase,
ferrisurite,
hemimorphite, mottramite,
plumbogummite and
vanadinite. The conditions of formation must have been relatively
basic because plumbophyllite is unstable in even weakly acidic environments.
Plumbophyllite forms prismatic crystals with wedge-shaped terminations that typically occur in divergent
sprays. Individual crystals are up to 3.0 × 0.3 × 0.2 mm3. Crystals are colourless to pale blue and
transparent with vitreous lustre
(AM 94.1198–1204).
Plumbophyllite from the Blue Bell Mine -
Image
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