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Formula: Na4Zn2Si7O18.5H2O
Hydrated tectosilicate (framework silicate), zeolite group,
zinc-bearing mineral
Crystal system: Orthorhombic
Specific gravity: 2.52 measured, 2.52 calculated
Hardness: 6
Streak: White
Colour: Colourless to pale mauve
Luminescence: Bright apple-green fluorescence under short wave UV, and a strong pale green cathodoluminescence under
an electon beam
Solubility: Does not readily dissolve in 1:1 hydrochloric acid but does show very slight etching after prolonged
exposure
Environments
Although gaultite was approved before 1994, to date (October 2025) it has been reported only from
the type locality.
Localities
At the type locality, the Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Québec,
Canada, gaultite occurs in a cavity in a single specimen taken from the centre of a 12 m3
inclusion of sodalite
syenite, approximately 5 m from a contact of
hornfels and
nepheline-sodalite
syenite. Associated minerals include
aegirine, analcime,
cancrinite, catapleiite,
chabazite, eudialyte,
galena, graphite,
lovozerite group minerals,
makatite, microcline,
nepheline, natrolite,
phillipsite,
polylithionite, pyrite,
serandite, sodalite,
steenstrupine-(Ce), ussingite,
villiaumite, vitusite-(Ce)
and
vuonnemite. Gaultite was the last of its paragenesis to form.
Gaultite occurs as euhedral, equant, multifaceted crystals up to 0.5 mm across, with an average size of 0.25
mm. It ranges in colour from colourless to pale mauve, and is invariably transparent
(CM 32.4.855-863).
Gaultite from the Poudrette Quarry -
Image
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