Fabrièsite

fabriesite

trinepheline

jadeite

banalsite

Images

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

Metamorphic 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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