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Formula: Na3(Ca5Na)Si16O36(OH)4F2.(14-x)H2O (x ≈ 5)
Phyllosilicate (sheet silicate), reyerite group
Crystal System: Triclinic
Specific gravity: 2.16 calculated for the empirical formula
Hardness: 2
Streak: White
Colour: Usually tan or creamy-yellow, but can also be colourless, light or dark green, or white
Luminescence: Pronounced bluish-white fluorescence under both long wave and medium wave UV, much less so
under short wave
Environments
Kodamaite is a relatively new mineral, approved in 2019.
Localities
At the type locality, the Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie,
Quebec, Canada, kodamaite was discovered in small cavities in
eudialyte-rich,
sodalite-syenite
xenoliths (sensu lato), frequently among the interstices in masses of
sodalite crystals. These xenoliths occur as large (up to several
metres in size), angular inclusions in
nepheline syenite, although those in which
kodamaite was found were tens of centimetres in size. The type specimen was collected in 1985 and was
recognised as a potentially new species. Subsequent to this, a richer discovery of the mineral was made in
1989 in a similar environment.
Minerals associated with kodamaite include
eudialyte group minerals,
aegirine, a
clinoamphibole,
natrolite, molybdenite,
pyrite, fluorite,
sodalite, catapleiite,
rinkite group minerals,
albite, villiaumite,
pyrochlore,
fluorapatite,
microcline and erdite.
Kodamaite generally occurs in spherulitic aggregates up to about 2 mm across, comprising thin, platy
to bladed crystals, with individual crystals averaging less than 0.05 x 0.5 mm.
Kodamaite is a late-stage mineral that developed under hydrothermal conditions at temperatures less
than 200°C, most likely under high to very high alkalinity. The interaction of these fluids with pre-existing
minerals, including pectolite,
eudialyte group minerals, and
sodalite, is likely essential to the formation of the
kodamaite
(CJMP 62.1.133-152).
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