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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,
phillipsite, vertumnite,
ettringite, garnet,
wollastonite, gypsum,
calcite, quartz and
hematite
(HOM).
Katoite from the Campomorto Quarry - Image
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