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Formula: Mg2Al3(AlSi5)O18
Cyclosilicate (ring silicate), hexagonal high-temperature paramorph of
cordierite
Crystal system: Hexagonal
Specific gravity: 2.512 measured for artificial material, 2.59 calculated
Hardness: 7 to 7½
Colour: Colourless in thin section
Common impurities: Fe,Mn,Na
Environments
Volcanic igneous environments
Metamorphic environments
Coal-seam fires
Localities
At Nickenicher Weinberg, Nickenich, Pellenz, Mayen-Koblenz, Rhineland-Palatinate, Germany, indialite has
been found with osumilite
(Mindat photo).
Indialite from Nickenicher Weinberg -
Image
At the type locality, the Bokaro coalfield, Ramgarh District, Jharkhand, India, indialite is formed by fusion
and recrystallisation of sedimentary rocks as a result of the burning of underlying coal seams. Associated minerals
include enstatite, magnetite,
labradorite, corundum and
glass
(HOM).
At Belvedere, Ercolano, Metropolitan City of Naples, Campania, Italy, indialite has been discovered in unusual
pyrometamorphic ejecta. The indialite-bearing xenoliths are composed of several pale yellow fragments
consisting of very fine-grained indialite with traces of
cristobalite. On the surface of the fragments, colourless
indialite and pale-blue, prismatic osumilite crystals form whitish
crusts, with subordinate phlogopite and trace amounts of
corundum. Gypsum and
iron-oxides are ubiquitous.
Indialite-bearing rocks originated through a pyrometamorphic process at shallow depth and at maximum
temperature close to ~1200°C
(AM 89.1-6).
At Unazuki, Kurobe City, Toyama Prefecture, Japan, indialite occurs in
cordierite veins in a polymetamorphosed pelitic rock. Associated minerals
include cordierite, andalusite,
sillimanite, biotite and
quartz
(HOM).
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