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Formula: Cu9S8
With oxidation states
Cu1+20Cu2+7(S2)2-7S2-10
(CM 23.61-76)
Sulphide, chalcocite-digenite group,
forms a series with chalcocite
Crystal System: Trigonal
Specific gravity: 4.89 calculated
Hardness: 2½
Colour: Bluish grey, black
Common impurities: Fe,Ag
Environments
Yarrowite is commonly associated with anilite,
bornite, chalcopyrite,
covellite, digenite,
djurleite, idaite,
tennantite and wittichenite
(Mindat).
Localities
At the type locality, Yarrow Creek, Yarrow Creek-Spionkop Creek deposit, Alberta, Canada, yarrowite occurs as a
replacement of other copper sulphides by selective removal of
copper. Yarrowite also replaces
spionkopite and
copper-iron sulfides. At the deposit
copper-bearing
sulphides include chalcopyrite,
bornite, spionkopite,
yarrowite, digenite,
djurleite, idaite,
wittichenite and tennantite.
Near-surface leaching of copper from the natural specimens produced the
following changes:
djurleite to anilite + Cu(aq) to
spionkopite + Cu(aq) to yarrowite + Cu(aq) to
covellite (minor) + Cu(aq)
(CM 18.511-518).
At the Clargillhead vein, Garrigill, Alston Moor, Eden, Cumbria, England, UK, yarrowite occurs as crystals
less than 1 micron in size, accompanied by similar sized zones of heavily tarnished unidentified blue copper sulphides,
interbanded with cerussite, some of which is associated with an
unidentified silver-bearing photosensitive phase.
Spionkopite occurs as rare grains in
cerussite and also in association with tarnished copper sulphides
(JRS 23.51).
At Rassal, Loch Kishorn, Highland, Scotland, UK, yarrowite occurs as a blue-grey to deep blue coarse flakes
in goethite. Associated minerals include
covellite and spionkopite
(JRS 15.56).
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