Formula: Pb7Cu2(SO4)4(SiO4)2(OH)2
Compound sulphate
Crystal System: Monoclinic
Specific gravity: 6.45 measured
Colour: Light green, yellow or bright yellowish-green
Solubility: Slowly soluble in cold hydrochloric or nitric acid
Environments
Localities
At the type locality, the Mammoth-Saint Anthony Mine, St. Anthony deposit, Tiger, Mammoth Mining District, Pinal county, Arizona, USA,
wherryite was found associated with chrysocolla,
diaboleite and paralaurionite. In 1943 a mining engineer
discovered a small vug of leadhillite crystals associated with
cerussite, anglesite,
phosgenite, paralaurionite,
hydrocerussite, diaboleite,
boleite, matlockite and
quartz. Within the cavity was some friable chalcocite with a
relict structure of the galena which it has replaced. The massive wall of the vug consisted of a
light-green fine granular mineral enclosing some chrysocolla, and at the cavity some
diaboleite and paralaurionite. This green matrix proved
to be a the new mineral wherryite, described in 1950. At the Saint Anthony deposit the basement rock is a
quartz monzonite, intruded by dikes of
aplite and by bodies of andesite
porphyry, now altered, as well as by later dikes and sills of
rhyolite and intrusive breccias of the earlier rocks.
Part of the paragenesis of the leadhillite vug may be interpreted as follows: A mass of
primary galena, close to the water table, was partly
replaced by chalcocite in the course of secondary
enrichment of the copper. Advancing oxidation altered some of the galena
to anglesite, which was gradually replaced by cerussite, while
some of the chalcocite was altering to chrysocolla. The
sequence, galena to anglesite to
cerussite, is the normal course of the weathering process. At some stage of this normal sequence, however,
a remarkable reversal took place with the formation of the complex sulphates leadhillite and
wherryite, as well as the formation of the rare basic carbonate hydrocerussite, and the rare
oxychlorides diaboleite and paralaurionite, and the
chlorofluoride matlockite. It may be that this unusual paragenesis was caused by an influx of solutions
containing chlorine ions. The wherryite has a fine granular texture and is usually intimately associated with
leadhillite, paralaurionite and
chrysocolla.
(AM 35.93-98).
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