pinacoid, pinakoid, a. and n. Cryst.
(ˈpɪnəkɔɪd)
[f. Gr. πίναξ, πινακ- slab: see -oid.]
A. adj. Applied to any plane, in a crystallographic system, intersecting one of the axes of co-ordinates and parallel to the other two. Opposed to octahedrid and prismatoid.
| 1895 Story-Maskelyne Crystallogr. ii. §18. |
B. n. A pinacoid plane, or a group of such planes constituting a ‘form’.
| 1876 Catal. Sci. App. S. Kens. §3470 A Polyhedron of Calcite, cut..so as to represent the optical characters..in directions perpendicular 1. To the pinakoid. 1881 Bauerman Text-bk. Syst. Min. 198 The octahedron, or unit pyramid, is always the largest, and the cube rectangular prism, or pinakoid, the smallest of the constituent forms. 1895 Story-Maskelyne Crystallogr. vii. §303 The poles of the pinakoids form the angular points of the systematic triangles. |
Hence pinaˈcoidal a., of the nature of or characteristic of a pinacoid.
| 1879 Rutley Study Rocks xiii. 245 A structural condition of pinakoidal separation. |