hemitropic, a. Cryst.
(hɛmɪˈtrɒpɪk)
[f. as prec. + -ic.]
Said of a composite or twin crystal: see quots.
| 1886 F. W. Rudler in Geol. Mag. III. 267 The edges of the hemitropic lamellæ are too blurred to allow the exact angles to be taken. 1895 Story-Maskelyne Crystallogr. §154 Two crystals are said to be hemitropic or twinned when, presenting identical forms, they are united together in such a way that, if we conceive one of them as being turned through half a revolution round a particular line which wil' be termed the twin-axis..corresponding faces and edges in the two crystals would become parallel. Ibid. §159 In the case of two hemitropic diplohedral crystals, the twin plane becomes in a crystallographic sense a plane of symmetry to the twin-structure; but..each crystal in the hemitropic group retains its individuality, notwithstanding the mutual interpenetration of the crystals. |