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Formula: [Pb8O2Zn(OH)6](S2O3)<4.2H2O
Thiosulphate (a salt of thiosuphuric acid H2S2O3)
Crystal System: Monoclinic
Specific gravity: 5.124 for the empirical formula and 5.123 for the ideal formula
Hardness: 2
Streak: White
Colour: Colourless
Luminescence: Not fluorescent under long or short wave UV
Solubility: In room-temperature dilute hydrochloric acid, hydroredmondite immediately becomes opaque and then
slowly dissolves
Environments
Metamorphic environments
Hydrothermal environments
Hydroredmondite is a new mineral, approved in 2021 and to date (January 2024) reported only from the type
locality.
Localities
At the type locality, the Redmond Mine, Waterville Lake, Haywood County, North Carolina, USA, the ore,
consisting mainly of galena and
sphalerite with lesser amounts of
chalcopyrite, occurs in an epithermal vein system consisting of
disconnected sulphide-bearing quartz lenses near the contact between a
granite gneiss and a
mica schist.
Redmondite, hydroredmondite and
sulfatoredmondite occur in a
secondary assemblage that comprises a variety of rare
lead - zinc -
copper sulphates, thiosulphates, and carbonates, including
bechererite, chenite,
elyite, fassinaite,
lahnsteinite, lanarkite,
lautenthalite, namuwite,
redgillite, osakaite,
sidpietersite, steverustite
and susannite, as well as some more common
secondary minerals such as
anglesite, brochantite,
caledonite, cerussite,
langite, leadhillite,
linarite, malachite,
posnjakite, schulenbergite
and wroewolfeite.
Redmondite, hydroredmondite and
sulfatoredmondite occur together in vugs in massive
galena - sphalerite -
chalcopyrite - quartz, in close
association with anglesite,
cerussite, chenite,
elyite, gypsum,
lanarkite, steverustite,
susannite, and several other potentially new minerals.
The formation (or preservation) of the new sulphate and thiosulphate minerals appears to have been limited to small vugs
within the galena-rich ore where exotic metal coordination complexes were
stabilised in stagnant solutions under supergene conditions. The
formation of rarer, more basic sulphate and carbonate minerals is thought to arise from the dearth of
pyrite in these types of epithermal
lead - zinc veins, limiting the formation
of sulphuric acid and allowing natural buffers to maintain a near-neutral pH (acidity) within groundwater and mine
runoff.
Hydroredmondite crystals occur as colourless, transparent prisms, blades, and tablets, up to about 1 mm in
maximum dimension, with an adamantine lustre.
(CJMP 61.1.189-202).
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