| 释义 |
pigeonite Min.|ˈpɪdʒənaɪt|
[f. the name of Pigeon Point in NE. Minnesota + -ite1.]
A silicate of magnesium, ferrous iron, and calcium, (Mg,FeII,Ca)(Mg,FeII)Si2O6, that is a monoclinic calcium-poor pyroxene substantially free of aluminium and ferric iron, and that is found chiefly in basic igneous, esp. volcanic, rocks.
1900A. N. Winchell in Amer. Geol. XXVI. 204 Since the anomalous condition was first discovered in the rocks from Pigeon point, it would be appropriate to call pyroxene thus optically abnormal pigeonite. 1931Amer. Jrnl. Sci. CCXXI. 405 The clino-pyroxenes.. form a continuous series of mix crystals, from diopside-rich (the phenocrysts are always diopsidic augites) to clino⁓enstatite- and hypersthene-rich (pigeonites). 1951Jrnl. Geol. LIX. 480/1 Pigeonites under plutonic conditions invert with cooling to orthopyroxenes. 1970Nature 25 Apr. 334/2 Interstitial pigeonite and augite in the lunar gabbroic anorthosite have Cr contents of 0·6 and 6·0 per cent respectively. 1975J. W. Frondel Lunar Mineral. ix. 217 Because of their chemical variability, exsolution textures, epitaxy with augite and orthopyroxene,..and relative abundance, lunar pigeonites have played a significant role in a reconstruction of the crystallization histories of mare basalts.
Hence pigeoˈnitic a.
1931Amer. Mineralogist XVI. 207 The groundmass pyroxene is often said to be of the pigeonitic variety (Holmatindur, Eskifjord; Vágsfjord, Faeroes; etc.). 1957Mineral. Mag. XXXI. 540 It is evident that the degree of inversion of the pigeonitic pyroxenes..must, in general, be correlated with the composition of the minerals as well as with their cooling history. 1972Contrib. Mineral. & Petrol. XXXV. 235 (heading) Variation of rare earth concentrations in pigeonitic and hypersthenic rock series from Izu-Hakone region, Japan. |