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Formula: Ca3Al2(OH)12
Hydroxide, ungrouped member of the garnet supergroup, forms a series
with grossular
Crystal System: Isometric
Specific gravity: 3.013 calculated
Hardness: 5 to 6
Streak: White
Colour: Colourless
Luminescence:
Solubility:
Common impurities: Mg,S
Environments
Volcanic igneous environments
Hydrothermal environments
Localities
At the Csódi Hill, Dunabogdány, Szentendre District, Pest County, Hungary, katoite has been found with about
37% grossular
(EJM 15.419-426).
At the type locality, the Campomorto Quarry, Pietra Massa Locality, Montalto di Castro, Viterbo Province, Lazio, Italy,
katoite occurs as a hydrothermal mineral in cavities in a
phonolitic lava flow that erupted through an argillaceous
marl. Associated minerals include
tobermorite, afwillite,
gehlenite, hydrocalumite,
opal, portlandite,
apophyllite, cordierite,
jennite, strätlingite,
chabazite, gismondine-Ca,
phillipsite, vertumnite,
ettringite, garnet,
wollastonite, gypsum,
calcite, quartz and
hematite
(HOM).
Katoite from the Campomorto Quarry - Image
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