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 (NaAlSi2O6áH2O),
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.
