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Formula: Cu6(SO4)(OH)10.H2O
Hydrated sulphate of copper, langite group
Crystal System: Monoclinic
Specific gravity: 3.45 measured and calculated
Hardness: 2
Streak: White
Colour: Pale green, grass-green, emerald-green, nickel-green
Solubility: Dissolves slowly in dilute hydrochloric acid
Environments
Redgillite is a secondary
supergene weathering mineral in oxidised
copper sulfide veins and post-mining environments, approved in 2003, although
it has been
known, but not formally approved, since the 1980s. Associated minerals include
covellite,
langite, wroewolfeite,
malachite, cuprite,
connellite and brochantite
(HOM, MW).
Localities
At Higher Roughton Gill (Balliway Rigg), Roughton Gill, Caldbeck, Allerdale, Cumbria, England, UK, redgillite
has been reported as acicular crystals up to 0.3 mm long with the characteristic light green colour, occurring rarely
in thin fractures in
sphalerite-rich veinstone with partly oxidised
copper sulphides. However,
montetrisaite, a
new higher hydrate of redgillite, has recently been approved, and it may be that the
redgillite reported from this locality is actually montetrisaite
(JRS 11.21-22).
At Red Gill mine, Roughton Gill, Caldbeck, Allerdale, Cumbria, England, UK, redgillite occurs as radiating
sprays of pale to
grass green acicular to long prismatic crystals which are usually less than 1 mm in length. It typically occurs in
thin fractures in
sulphide-rich matrix associated with other copper sulphate minerals, notably
langite, and is probably post-mining in origin
(JRS 11.41-42).
At the type locality, Silver Gill (NOT Red Gill), Roughton Gill, Caldbeck, Allerdale, Cumbria, England, UK,
redgillite occurs as translucent
to transparent grass-green bladed crystals up to 0.15 mm long with squared-off or tapering terminations, usually in
radiating groups.
It is typically found in thin fractures in partly oxidised sulphides where it is commonly associated with
langite and more rarely with
malachite,
cuprite, connellite and
brochantite
(MM 69.6.973–980).
The Silver Gill vein is a lead-, zinc-
and copper- bearing quartz vein.
The mineralisation is thought to be early
Carboniferous in age
(Mindat).
At Eaglebrook mine, Tal-y-bont, Ceulanymaesmawr, Ceredigion, Wales, UK, redgillite occurs as green laths, and
also as
scattered acicular to lathlike crystals and radial sprays to 1 mm, on corroded
primary sulphide matrices, and often separated from
the primary sulphide by a thin film of
covellite. Associated minerals include
brochantite and an uncharacterised mid-blue finely botryoidal phase
(MW).
At the Esgair Hir mine, Tal-y-bont, Ceulanymaesmawr, Ceredigion, Wales, UK, redgillite was found associated with
langite and covellite on corroded
chalcopyrite. Scattered redgillite laths can cover areas to
several square
centimetres; sprays of crystals to 1 mm have also been noted
(MW).
At the Llywernog mine, Ponterwyd, Cwmrheidol, Ceredigion, Wales, UK, redgillite occurs as green laths
(MW).
At Bwlchrhennaid mine, Pen-bont Rhydybeddau, Trefeirig, Ceredigion, Wales, UK, redgillite occurs as lathlike
crystals to
0.3 mm in size
(MW).
At the Daren mine, Pen-bont Rhydybeddau, Trefeirig, Ceredigion, Wales, UK, redgillite occurs as green crystals
(MW).
At the Llechwedd Helyg mine, Pen-bont Rhydybeddau, Trefeirig, Ceredigion, Wales, UK, redgillite occurs as green
laths
(MW).
At the Frongoch mine, Pontrhydygroes, Upper Llanfihangell-y-Creuddyn, Ceredigion, Wales, UK, redgillite occurs
rarely as small
groups of divergent green laths in association with langite,
schulenbergite, caledonite,
hemimorphite and
hydrocerussite
(MW).
At the Hendre Felen mine, Ysbyty Ystwyth, Ceredigion, Wales, UK, redgillite occurs as tufts of acicular green
crystals to
0.5 mm in size associated with an uncharacterised blue substance
(MW).
At the Dylife Mine, Dylife, Machynlleth, Powys, Wales, UK, redgillite occurs as green laths associated with
serpierite and wroewolfeite
(MW).
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