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Formula: Fe2+Al3O2(BO3)(SiO4)
Nesosilicate (insular SiO4 groups), borosilicate
Crystal System: Orthorhombic
Specific gravity: 3.169 calculated
Hardness: 7
Streak: Pale blue
Colour: Blue
Environments
Plutonic igneous environments
Pegmatites
Metamorphic environments
Localities
At Horní Bory, Bory, Žďár nad Sázavou District, Vysočina Region, Czech Republic, omonelite occurs in
borosilicate-bearing veinlets cutting light-coloured
granulite. Associated minerals include
grandidierite, werdingite,
boralsilite, K-feldspar,
quartz and plagioclase
(HOM).
At the type locality, the Misen River, Omine Mountains, Tenkawa village, Yoshino district, Nara Prefecture, Japan,
ominelite occurs as grains in close association with sekaninaite,
garnet, biotite,
andalusite, topaz,
K-feldspar, plagioclase,
muscovite, quartz,
dumortierite, schorl,
zircon, ilmenite,
apatite, monazite and
pyrite in a porphyritic
granite of Miocene age (23.03 to 5.333 million years ago) exposed along
the river. Temperatures less than 700°C and pressures below 4 kbars are suggested for the formation of ominelite
and associated sekaninaite, topaz,
andalusite and dumortierite.
The aluminium-rich minerals could be either magmatic or restitic in origin
(Restite is the residual material left at the site of melting during the in-place production of magma - Wiki)
(AM 87.160-170).
Ominelite from the Misen River - Image
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