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Formula: [Cu4Al2(OH)12](CO3).3H2O
Valence: [Cu2+4Al2(OH)12](CO3).3H2O
Hydrated carbonate of copper,
hydrotalcite supergroup
Crystal system: Monoclinic
Specific gravity: 2.825 calculated for the empirical formula
Streak: Light blue
Colour: Blue
Luminescence: Does not fluoresce under short wave or long wave UV
Environments
Marioantofillite is a new mineral, approved in 2025 and to date (December 2025) reported only from the type locality.
Localities
At the type locality, the Monte Copello-Reppia mine, Reppia, Ne, Genoa, Liguria, Italy, the
copper-iron ore bodies are stratiform and are located at the contact between
serpentinite and
pillow basalts or at the interface between
brecciated basalts and the
sedimentary cover represented by cherts and
limestone; finally, stockwork veins protrude from the ore bodies downward
within the brecciated basalts.
The Monte Copello prospect exploited a sulphide ore body, mainly represented by
pyrite and chalcopyrite within a
gangue of calcite,
quartz and clay minerals, at the
tectonised contact between basalts and
limestone. The ore body is deeply weathered, and it is represented by
gossan. Several
supergene phases have been observed within its vugs. Observed
species include allophane,
brochantite,
carbonatecyanotrichite,
connellite, chrysocolla,
cuprite, delafossite,
felsőbányaite (?), gypsum,
langite, malachite and
native copper.
Marioantofillite occurs as globular aggregates, up to 1 mm across, sometimes showing µm-sized prismatic crystals.
The colour is blue, and the streak is light blue. Lustre is greasy. The mineral is transparent, soft and brittle. In the
type material, marioantofillite is associated with allophane and
malachite on limonite. Its genesis is
related to the oxidative dissolution of the primary
copper ores by mine drainage aqueous solutions and neutralisation by
gangue carbonates
(EJM 37.5.733-746).
Marioantofillite from the Monte Copello-Reppia
Mine - Image
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