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Formula: Na2TiO(SO4)2.2H2O
Sulphate, titanium-bearing mineral
Crystal System: Orthorhombic
Specific gravity: 2.45 calculated for the empirical formula
Hardness: 3
Colour: Crystals colourless, aggregates white
Luminescence: Not fluorescent under ultraviolet light or an electron beam
Environments
Calamaite is a relatively new mineral, approved in 2016 and to date (February 2024) reported only from the
type locality.
Localities
The type locality, the Alcaparrosa Mine, Sierra Gorda, Antofagasta Province, Antofagasta, Chile, is an abandoned
sulphate mine. The deposit contains veins and lenses consisting of diverse iron
sulphates and formed as a result of the oxidation of pyrite ore under the
extremely arid conditions of the Atacama Desert. The pyrite-rich orebodies
are located in volcanic rocks mainly consisting of andesite and
dacite. The mine was worked mainly for
römerite and coquimbite as raw
materials for sulphuric acid, but there was no copper or other commercially
profitable metals. The mine, however, is famous as a source of numerous museum-quality specimens of many
iron sulphates.
Specimens with calamaite were collected in January 2016 in an old underground working, in a
römerite-enriched cavernous zone located inside a sulphate body mainly
composed of coquimbite. Numerous cracks and cavities in a massive
ferricopiapite – römerite
– coquimbite rock are encrusted here with
coquimbite and römerite
crystal crusts. Other minerals found here are metavoltine,
tamarugite, halotrichite,
szomolnokite, rhomboclase
and, in minor amounts, ferrinatrite,
krausite and calamaite. The
supergene mineralisation also includes
magnesiocopiapite,
copiapite, butlerite,
parabutlerite, voltaite,
pertlikite,
alcaparrosaite, alunogen,
natrojarosite, gypsum,
cadwaladerite and opal.
Pyrite, quartz,
plagioclase and rutile are
relict minerals. Native sulphur occurs as a product of the first step of
supergene alteration of
pyrite.
Calamaite occurs in cavities of open-work sulphate aggregates mainly consisting of red-brown
römerite; it overgrows römerite
or forms intimate intergrowths with it, as well as with coquimbite and
metavoltine. Calamaite typically forms thin, acicular to
hair-like crystals up to 2 mm long and up to 0.01 mm thick combined in bunches or radial spherulitic clusters up to
4 mm across. Calamaite is transparent, colourless in separate crystals and white in aggregates, with a
vitreous lustre
(EJM 30.4.801-809).
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