orthic, a. Min.
(ˈɔːθɪk)
[f. Gr. ὀρθ-ός straight + -ic.]
Having the cleavage-planes at right angles to one another: = orthoclastic.
| 1877 Le Conte Elem. Geol. (1879) 204 note, In this case syenite would differ from diorite only in the form of the feld⁓spar, which in the former is orthic (orthoclase), and in the latter clinic (plagioclase). |