plagioclase Min.
(ˈpleɪdʒɪəʊkleɪs)
[Named 1847, f. plagio- + Gr. κλάσις fracture, cleavage.]
(See quot. 1868.)
| 1868 Dana Min. (ed. 5) Suppl. 802 Plagioclase, Breithaupt's name for the group of triclinic feldspars, the two prominent cleavage directions in which are oblique to one another. 1879 Rutley Stud. Rocks x. 91 In the case of plagioclase the crystals exhibit numerous bands of different colours. 1903 Geikie Text Bk. Geol. (ed. 4) I. ii. 200 The Plagioclase rocks. 1941 Proc. Prehist. Soc. VII. 61 Sparsely distributed small phenocrysts of turbid plagioclase felspar. 1959 C. S. Hurlbut Dana's Man. Min. (ed. 17) v. 495 The plagioclase feldspars, also called the soda-lime feldspars, form a complete solid-solution series from pure albite, NaAlSi3O8, to pure anorthite, CaAl2Si2O8. 1971 Sci. Amer. Oct. 50/3 The plagioclase in the moon rocks..is almost pure anorthite (CaAl2Si2O8). |