| 释义 |
magnesiochromite, n. Min.|mægˌniːzɪəʊˈkrəʊmaɪt|
[f. *magnochromite n. after magnesioferrite n.]
Orig., a mineral, (Mg,Fe)Cr2O4 , analogous to chromite ( FeCr2O4 ), with magnesium replacing much of the iron. Now usu., a spinel of the general formula (Mg,Fe)(Cr,Al)2O4 , spec. the end-member picrochromite, MgCr2O4 .
1892E. S. Dana Dana's Syst. Min. (ed. 6) 228 The iron may be replaced by magnesium as in magnochromite (magnesiochromite) below. 1913Mineral. Mag. XVI. 364 Magnesiochromite.., the same as magnochromite (G. M. Bock, 1868). A variety of chromite containing magnesium, (Fe,Mg)Cr2O4 . 1929Amer. Mineralogist XIV. 355 Chromite is usually a combination of the pure chromite molecule plus the so-called magnesiochromite of Bock, hercynite and spinel. Magnesiochromite represents a spinellid that stands between spinel and chromite. 1976Earth & Planetary Sci. Lett. XXIX. 12/2 By far the most common type of spinels observed are magnesiochromites. Ibid., Magnesiochromites have Cr as the dominant trivalent cation and Mg2+>Fe2+ . Ibid. 19/1 The three spinel groups closely reflect the gross chemical nature of the basalts: magnesiochromites are found in olivine-normative tholeiites, chromian spinels in Al2O3 -rich picrite and titaniferous magnesiochromites in olivine basalt with pronounced alkaline affinities. 1992W. A. Dear et al. Introd. Rock-Forming Minerals (ed.2) 568 In general terms the magnesiochromites and the chromites (sensu stricto) have the same paragenesis, the commonest member of the series probably being ferroan magnesiochromite. |