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Formula: CaFe3+Fe2+2O(Si2O7)(OH)
Sorosilicate, lawsonite group
Crystal System: Orthorhombic
Specific gravity: 3.99 to 4.05 measured, 4.064 calculated
Hardness: 5½ to 6
Streak: Black, inclining to green or brown
Colour: Iron-black, dark grayish black
Solubility: Gelatinises with hydrochloric acid
Common impurities: Mg,Mn
Environments:
Plutonic igneous environments
Metamorphic environments
Hydrothermal environments
Ilvaite is a rare sorosilicate primarily found in iron-rich metamorphosed
limestone and
dolostone or zinc and
copper deposits; less commonly it is found as a minor mineral in
mafic and ultramafic rocks either as a late-stage
primary mineral or as the result of hydrothermal alteration
(Mines & Minerals 25.39). It also occurs in sodalite -
syenite and in
zeolites
(Webmin, Dana).
Associated minerals include quartz, magnetite,
hedenbergite, sphalerite and
fluorite
(HOM).
Localities
The Two Mile and Three Mile deposits, Paddy's River, Paddys River District, Australian Capital Territory, Australia,
are skarn deposits at the contact between
granodiorite and volcanic rocks.
Ilvaite is a primary silicate that occurs rarely with
quartz, magnetite,
andradite and nontronite at the
Two Mile deposit
(AJM 22.1.35).
At Fengjiashan, Hubei, China, ilvaite occurs on quartz or
calcite
(MinRec 38.1.37).
In the Deccan traps of India, ilvaite is found only in the basalt
of the Kurar quarry, Bombay-Malad, growing
on quartz and second-generation calcite,
but even there it is infrequent.
It is associated with quartz, calcite,
hematite, pumpellyite and rarely
andradite, but never with babingtonite or
julgoldite
(MinRec 34.1.50).
At the type locality, Torre di Rio - Santa Filomena area, Elba Island, Italy, ilvaite occurs as
aggregates with pyroxene and dolomite
(Dana).
At the Los Remedios mine, Taxco mining district, Mexico, ilvaite has been found with overgrowths of
rhodochrosite and fluorite
(MinRec 42.5.430).
At Dalnegorsk, Russia, hedenbergite
pseudomorphs after ilvaite have been found
(KL p229).
At Whin Sill, Teesdale, England, UK, ilvaite has been found in
mafic-pegmatite
veinlets, associated with
ilmenite, titanite and
apatite.
The ilmenite may form pseudomorphs
after titaniferous
magnetite. The ilvaite encloses small grains of
zircon,
rutile, pyrrhotite,
chalcopyrite and sphalerite
(M&M 25.39).
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