Blairmorite Explained

Blairmorite
Type:	Extrusive igneous
Type Link:	Volcanic rock
Composition:	Analcime, sanidine, pyroxene
Composition Secondary:	Titanite, melanite, nepheline

Blairmorite is a very rare^[1] porphyritic volcanic rock named after the community of Blairmore in southwestern Alberta, Canada.^{[2] [3]} It is characterized by dominant analcime phenocrysts in a matrix of analcime, sanidine and alkalic pyroxene with accessory titanite, melanite and nepheline. It is a leucocratic variety of analcimite (a foidite).^[4] Blairmorite has also been described as an analcime-rich variety of phonolite.^{[5] [6]}

This extrusive igneous rock is known from only two geological formations worldwide. The foremost blairmorite occurrence is the Crowsnest Formation in the Canadian province of Alberta where it is associated with agglomerates and tuffs from explosive eruptions. The other locality is the Lupata Gorge in Mozambique.^[2]

Notes and References

1. Book: Atlas of igneous rocks and their textures . Longman . MacKenzie, W.S., Donaldson, C.H. and Guilford, C. . 1982 . Harlow . 121 . 0-582-30082-7.
2. Pearce. T.H.. Analcime phenocrysts in igneous rocks: Primary or secondary? – Discussion.. American Mineralogist. 78. 225–229. 1993.
3. Johannsen, A. 1933. A descriptive petrography of the igneous rocks, Appendix III, p. 244. Univ. of Chicago Press.
4. Book: Igneous Rocks — A Classification and Glossary of Terms . Cambridge University Press . Le Maitre, R.W. (editor) . 2002 . Cambridge . 55, 64 . 0-521-66215-X. 2nd .
5. Book: Analcite-bearing igneous rocks from the Crowsnest Formation, southwestern Alberta (Current Research report 93-B1) . Geological Survey of Canada . T.D. . Peterson . K.L. . Currie . 1993 . 51–56.
6. Book: An Introduction to the Rock-Forming Minerals . Mineralogical Society . W.A. . Deer . R.A. . Howie . J. . Zussman . 2013 . London . 9780903056274. 3rd .