| 释义 |
howardite|ˈhaʊədaɪt|
[f. the name of Edward Howard (fl. 1802), English chemist: see -ite1.]
1. Min. A supposed silicate of iron and magnesium found in some meteorites.
1848C. U. Shepard in Amer. Jrnl. Sci. VI. 253 The earthy constituent of this stone, like that of the Iowa meteorite..appears to be a tersilicate of the protoxyd of iron and magnesia, a mineral which though frequent in meteoric stones, has never yet been distinctly recognized, and which in a future paper on American Meteorites, I shall more particularly describe under the name of Howardite, after the Hon. Mr. Howard, that celebrated chemist, who was the first British writer whose labors contributed to elucidate the history of these extra⁓terrestrial bodies. 1955M. H. Hey Index Min. Species (ed. 2) 127 Howardite (of Shepard). A doubtful meteoritic silicate of Fe and Mg.
2. Astr. [ad. G. howardit (G. Rose 1863, in Physikal. Abhandl. d. K. Akad. d. Wiss. zu Berlin 29).] Any of a group of achondritic meteorites principally composed of hypersthene and anorthite.
1881L. Fletcher Guide Coll. Meteorites (Brit. Mus.) 17 Perhaps for those aerolites which contain little or no nickel-iron the division into Howardites, Eukrites, Chladnites, Chassignites, Shalkites, and Carbonaceous is the most convenient. 1915O. C. Farrington Meteorites iii. 35 Of a total of nine meteorites belonging to the class of howardites, five have fallen in Russia. 1916Mineral. Mag. XVIII. 36 The angrites, nakhlites, howardites, eucrites, and sherghottites..are richer in lime..than chondritic stones generally. 1971B. Mason in I. G. Gass et al. Understanding Earth viii. 117 (table) [Achondrites are] sometimes divided into calcium-poor achondrites (aubrites, diogenites, chassignite, ureilite) and calcium-rich achondrites (angrite, nakhlite, howardites, eucrites). |