Pigeonite
| Pigeonite | ||
|---|---|---|
2V angle 0 – 30° measured | | |
| Dispersion | weak to distinct | |
| References | [2][3][4] | |
Pigeonite is a mineral in the
clinopyroxene subgroup of the pyroxene group. It has a general formula of (Ca,Mg,Fe)(Mg,Fe)Si2O6. The calcium
cation fraction can vary from 5% to 25%, with iron and magnesium making up the rest of the cations.
Pigeonite crystallizes in the
orthopyroxene. The low-temperature limit of pigeonite stability depends upon the Fe/Mg ratio in the mineral and is hotter for more Mg-rich compositions; for a Fe/Mg ratio of about 1, the temperature is about 900 °C. The presence of pigeonite in an igneous rock thus provides evidence for the crystallization temperature of the magma
, and hence indirectly for the water content of that magma.
Pigeonite is found as
exsolution lamellae of calcic clinopyroxene,[5] leaving no pigeonite present.[6] Textural evidence of its breakdown to orthopyroxene plus augite may be present, as shown in the accompanying microscopic
image.
Pigeonite is named for its type locality on Lake Superior's shores at Pigeon Point, Minnesota, United States. It was first described in 1900.[4][7]
References
- S2CID 235729616.
- ^ http://rruff.geo.arizona.edu/doclib/hom/pigeonite.pdf Handbook of Mineralogy
- ^ http://www.webmineral.com/data/Pigeonite.shtml Webmineral data
- ^ a b http://www.mindat.org/min-3210.html Mindat.org
- ^ "Calcic Clinopyroxene".
- ^ Nesse, William (2012). Introduction to Mineralogy (Second ed.). Oxford University Press. p. 300.
- ^ Winchell, Alexander N. (1900). "Mineralogical and petrographic study of the gabbroid rocks of Minnesota, and more particularly, of the plagioclasytes". The American Geologist. 26 (4): 197–245.