BLAIRMORITE

 

Blairmorite is a rare type of volcanic lava.  It is known principally from an old, eroded alkaline volcanic center near Blairmore, far-southwestern Alberta, Canada  There, blairmorite is one of several specific volcanic rock types in the Crowsnest Formation (a.k.a. Crowsnest Volcanics).  The original volcano was active during the mid-Cretaceous, at about 100 m.y.

 

Blairmorites are a specific variety of porphyritic phonolites having phenocrysts of analcime (NaAlSi2O6·H2O), one of the feldspathoid minerals.  Crowsnest blairmorites have reddish analcime phenocrysts that vary in luster from glassy to dull, depending on the degree of weathering and alteration.  The analcime crystals are frequently euhedral (fully formed crystals having all faces present).  Other phenocrysts observed in these blairmorites are melanite garnet, clinopyroxene, and sanidine feldspar.  The finely-crystalline matrix material typically consists of the same suite of minerals.

 

Blairmorite (porphyritic analcime phonolite) (above & below; above: 7.8 cm across; below: 2.2 cm across) from the Crowsnest Formation near Blairmore, Alberta, Canada.

Red = analcime

Black = melanite garnet

Creamy white = sanidine feldspar

Green matrix = mostly clinopyroxene. 

 


 

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