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Formula: Ba2Ca(BSi2O7)2
Cyclosilicate (ring silicate), hyalotekite group,
barium- and boron- bearing mineral
Crystal System: Tetragonal
Specific gravity: 3.644 calculated for the empirical formula
Hardness: 5½
Streak: White
Colour: Colourless and light blue to medium greenish blue
Luminescence: Not fluorescent under UV
Solubility: Slowly decomposes in concentrated hydrochloric acid (after about 1 hour) and unreactive in concentrated
sulphuric acid (after days).
Environments
Itsiite was approved in 2013, but to date (December 2024) it has been reported only from the Gun Claim.
Localities
At the type locality, Trench 1, Gun claim, Wilson Lake, Itsi Mountain, Watson Lake mining district, Yukon, Canada,
the holotype specimen of itsiite was collected in 1984, but not identified as a new mineral until 2013. The Gun
claim is a barium-rich skarn deposit
associated with a quartz
monzonite. The minerals found at the Gun claim include
alforsite, baryte,
cerchiaraite-(Al),
cerchiaraite-(Fe), diopside,
gillespite, pellyite,
pyrite, quartz,
sanbornite, sphalerite,
taramellite and witherite.
Itsiite occurs in low-temperature, late-stage veins in direct association with
cerchiaraite-(Fe), diopside,
pyrite, quartz,
sphalerite and witherite. Crystals
are commonly heavily included with cerchiaraite-(Fe).
Itsiite occurs as intergrowths of colourless and light blue to medium greenish-blue tetragonal plates up to 1 mm
across. The plates are flattened and generally striated
(CM 52.3.401-407).
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