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Formula: NaLiZrSi6O15
Inosilicate (chain silicate), double chains, tuhualite group,
lithium- and
zirconium- bearing mineral
Crystal system: Orthorhombic
Specific gravity: 2.79 measured, 2.80 calculated
Hardness: ~6
Streak: White
Colour: Colourless to pink, cream, white, commonly zoned
Luminescence: Fluoresces light yellow under short wave UV, no fluorescence under long wave, and no phosphorescence
under either wavelength
Common impurities: Ti,Hf
Environments
Localities
At the type locality, Washington Pass, Golden Horn Batholith, Okanogan County, Washington, USA, the batholith
exists in three compositional phases. The oldest phase hosts the zektzerite and is a
riebeckite granite
consisting of quartz,
riebeckite and perthite.
It commonly displays miarolitic and granophyric texturos and is believed to have crystallised at a shallow depth at
pressures between 0.5 and 1.0 kbar. Calcium and magnesium are nearly absent, and aluminum is present in quantities
slightly below that of a normal granite. The lithium content,
however, is somewhat higher than that of a typical granite, and the
riebeckite may contain up to 1290 ppm lithium.
The remaining phases in the batholith are more normal granites
containing biotite,
hastingsite, hornblende,
plagioclase, orthoclase
and quartz.
Zektzerite has been found in less than fifty miarolitic cavities occurring both in situ and in talus
boulders along a narrow three mile belt in the riebeckite
granite. Zektzerite-bearing pockets are usually small,
from 2 to 10 cm in their longest dimension and clay-free. Typical
zektzerite crystals are from 4 to 15 mm across and occur several to a pocket, loose or scattered upon white
microcline and associated with lustrous
smoky quartz crystals up to 6 cm long, well formed
riebeckite crystals up to 3 cm long, and tiny euhedral
zircon crystals.
Astrophyllite, elpidite
and aegirine are also found as associated minerals in the miarolitic
cavities. Unusual pockets may yield over a dozen zektzerite crystals ranging in size up to 2.5 cm.
The pocket of the type material contained a slightly etched crystal 3.7 X 3.5 X 1.5 cm3, the largest
one found as of 1977.
Zektzerite crystals are colorless to pink, have a white streak, and may exhibit colour zoning. Many
crystals show translucent interiors which are pink, colourless, or cream-coloured, and which are surrounded by a
whitish chatoyant zone 1 to 2 mm thick on prism and pinacoid faces. The lustre on cleavage surfaces and fracture
surfaces is vitreous
(AM 62.415-420).
Zektzerite from Washingto Pass -
Image
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