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Formula: Na3Al3Si3O12.2H2O
Hydrated tectosilicate (framework silicate), zeolite family
Crystal System: Orthorhombic
Specific gravity: 2.386 calculated
Hardness: 5 to 5½
Streak: White
Colour: White to pale yellow
Luminescence: Not fluorescent under UV
Common Impurities: Ca,K,Ba,Mg,Fe,Mn
Environments
Fabrièsite is a relatively new mineral, approved in 2012.
Localities
At the type locality, Tawmaw, Hpakant-Tawmaw Jade Tract, Hpakant Township, Mohnyin District, Kachin State,
Myanmar, two new (in 2012) mineral species, trinepheline and
fabrièsite are found in late-stage metamorphic veins of the jadeite
deposit, in serpentinised
peridotite and related to the hydration of
trinepheline. They occur intimately intergrown together with
nepheline, and more rarely with
albite and other feldspar group
phases such as banalsite and
stronalsite; other associated minerals are
jadeite and
secondary products like
natrolite and harmotome.
Both fabrièsite and trinepheline are
pseudomorphs after jadeite and
occur as skeletal allotriomorphic (not having their own regular shape, as determined by their internal structure, but
being shaped instead by adjacent minerals) crystals up to 20 μm long and 10 μm wide. They are white to yellowish in
hand specimens, colourless in thin section; the streak is white and the lustre appears vitreous to greasy
(EJM 26.257-263, HOM).
Fabrièsite from Tawmaw - Image
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