Blairmorite

{{short description|Rare porphyritic volcanic rock}}

{{Infobox rock

|name= Blairmorite

|alternative_name=

|type= Extrusive igneous

|type_link= Volcanic rock

|image= Blairmorite_from_the_Crowsnest_Formation.jpg

|image_size= 250

|alt=

|caption= A specimen of blairmorite from the Crowsnest Formation. The amber mineral is analcime, the pale mineral is sanidine and the small black minerals are melanite garnet.

|coordinates=

|composition= Analcime, sanidine, pyroxene

|composition_secondary= Titanite, melanite, nepheline

}}

Blairmorite is a very rare{{cite book | title=Atlas of igneous rocks and their textures | publisher=Longman | author=MacKenzie, W.S., Donaldson, C.H. and Guilford, C. | year=1982 | location=Harlow | pages=121 | isbn=0-582-30082-7}} porphyritic volcanic rock named after the community of Blairmore in southwestern Alberta, Canada.{{cite journal|last=Pearce|first=T.H.|title=Analcime phenocrysts in igneous rocks: Primary or secondary? – Discussion.|url=http://www.minsocam.org/ammin/AM78/AM78_225.pdf|journal=American Mineralogist|volume=78|pages=225–229|year=1993}}Johannsen, A. 1933. A descriptive petrography of the igneous rocks, Appendix III, p. 244. Univ. of Chicago Press. 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).{{cite book | title=Igneous Rocks — A Classification and Glossary of Terms | publisher=Cambridge University Press | author=Le Maitre, R.W. (editor) | year=2002 | location=Cambridge | pages=55, 64 | isbn=0-521-66215-X| edition=2nd }} Blairmorite has also been described as an analcime-rich variety of phonolite.{{cite book | url=http://publications.gc.ca/collections/collection_2017/rncan-nrcan/M44-93-1B.pdf | title=Analcite-bearing igneous rocks from the Crowsnest Formation, southwestern Alberta (Current Research report 93-B1) | publisher=Geological Survey of Canada | first1=T.D. | last1=Peterson | first2=K.L. |last2=Currie | year=1993 | pages=51–56}}{{cite book | title=An Introduction to the Rock-Forming Minerals | publisher=Mineralogical Society | first1=W.A. | last1=Deer | first2=R.A. | last2=Howie | first3=J. | last3=Zussman | year=2013 | location=London | isbn=9780903056274| edition=3rd }}

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.