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Formula: Co2(CO3)(OH)2
Carbonate of cobalt,
rosasite group
Crystal System: Monoclinic
Specific gravity: 3.970 calculated for the empirical formula
Hardness: 4
Streak: White
Colour: Orange-pink
Luminescence: Not fluorescent under long wave, medium wave or short wave UV
Solubility: Soluble in cold hydrochloric or nitric acid with effervescence
Environments
Perchiazziite is a new mineral, approved in 2023 and to date reported only from the type locality.
Localities
The type locality, the Mt. Ramazzo Mine, Borzoli, Genoa, Genoa, Liguria, Italy, is located in the Sestri-Voltaggio
ophiolitic complex, which is hosted in
serpentinised ultramafic
rocks close to the contact with pillowed dolerite. The
primary ores are mainly
pyrite, pyrrhotite,
chalcopyrite, hematite and
magnetite. They have undergone
supergene alteration, resulting in the presence of many
secondary minerals, including sulphides such as
covellite and digenite, oxides and
hydroxides such as opal, goethite and
heterogenite, carbonates such as
azurite, artinite,
hydromagnesite and
nesquehonite, sulphates such as
brochantite, chalcanthite,
epsomite, gypsum and
melanterite, and silicates such as
chrysocolla. The Monte Ramazzo Mine is also the type locality for
ramazzoite, and it is also known as an occurrence of the minerals of the
rosasite group, including
malachite, kolwezite and
mcguinnessite, as well as perchiazziite.
Perchiazziite occurs as globular aggregates up to 0.1 mm in diameter, composed of very thin fibres. These develop
on a matrix composed mostly of goethite and
magnetite, in association with
calcite and cobalt-bearing
malachite. Aggregates of perchiazziite are pale orange-pink on their
outer surfaces but white in thin section. It is translucent with a white streak and silky lustre.
Perchiazziite is of supergene origin, possibly having been
formed as a result of the oxidation of cobalt-bearing sulphides
(pyrite, chalcopyrite and
pyrrhotite), hydroxides
(heterogenite), and carbonates
(spherocobaltite), which occur in
serpentinite rocks
(CJMP 62.2.369-378).
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