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Formula:
(Na,☐)12(☐,Na)12Sr12Zr14(Si3O9)10[Si2BO7(OH)2]6.12H2O
Cyclosilicate (ring silicate), zirconium-bearing mineral
Crystal System: Trigonal
Specific gravity: 3.16 calculated and 3.12 for the empirical formula
Hardness: 5½
Streak: White
Colour: Grey to brown
Luminescence: No fluorescence under long wave or short wave UV
Solubility: Does not effervesce in 1:1 hydrochloric acid at room temperature
Common impurities: Ba,Hf
Environments
Plutonic igneous environments
Pegmatites
Localities
At the type locality, the Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Quebec,
Canada, bobtraillite was originally discovered in green vuggy zones of
breccia blocks.
The majority of bobtraillite specimens have been recovered from igneous
breccia, but the mineral has also been encountered rarely in
cavities in pegmatites in
nepheline syenite.
Bobtraillite is a late-stage phase; associated minerals include a fibrous white
burbankite group mineral, green
donnayite-(Y), a green acicular to prismatic monoclinic
amphibole, white, blocky
albite, aegirine,
pyrrhotite, pyrite,
annite, analcime,
microcline, a white mica
(possibly muscovite), yellow
titanite, and calcite.
Bobtraillite occurs in thin, discontinuous pockets, two to four millimeters wide, intimately associated with
blocky albite, green amphibole
and calcite. The pocket margins also contain rounded aggregates of
sulphides and there are indications that the matrix material contains
nepheline, albite,
microcline, annite, a white
mica and a clinopyroxene inferred
to be aegirine.
Crystals of bobtraillite are blocky to prismatic, up to 2 mm in size. Very rarely are crystals found as
plates. The mineral generally occurs as isolated single crystals or simple parallel intergrowths with two or three
members, rarely in small rosettes less than 0.1 mm across. It is most commonly grey to pale green or brown in
colour and, very rarely, almost black. One characteristic is the presence of dark greenish to black rims, the
colouration of which is most likely due to inclusions of clinoamphibole
(CM 43.2.747-758).
At the Saima complex, Kuandian County, Dandong, Liaoning, China,
gysinite-(La), new in 2022, has been discovered in
lujavrite in interstices or enclosed in
microcline, aegirine and
nepheline. Associated minerals include
nepheline, aegirine,
microcline, natrolite,
eudialyte, lamprophyllite,
bastnäsite-(Ce),
parisite-(Ce),
ancylite-(La),
ancylite-(Ce), bobtraillite,
britholite-(Ce), thorite,
calcite and galena
(MM 87.1.143–150).
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