Here's an unusual rock that represents a cavity-filling in a pegmatitic syenite.  The syenite host rock is dominated by large, whitish albite crystals (= sodium plagioclase feldspar, NaAlSi3O8) (see left & right edges of photo).  The cavity fill has nice, large, bluish sodalite crystals (= sodium chloro-aluminosilicate, Na8(AlSiO4)6Cl2)).  Surrounding each sodalite is a radiating spray of very dark green needles of aegirine pyroxene (= sodium iron silicate, NaFeSi2O6).


The rock comes from southeastern British Columbia's Ice River Complex.  The Ice River is an 18-kilometer long, 29-square kilometer, backward J-shaped alkaline igneous intrusion emplaced in Cambro-Ordovician passive-margin limestones and shales.


Age: ~356 million years (Tournaisian Stage, Early Mississippian or Famennian Stage, Upper Devonian, depending on which geologic time scale one uses)


Sodalite-aegirine-albite pegmatite (field of view ~7.1 cm across) from the Ice River Complex of British Columbia, Canada.

Blue = sodalite

Very dark green = aegirine pyroxene

Whitish = albite/sodium plagioclase feldspar



Rock info. from Tony Peterson.




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