anhedraladj.

1898 Amer. Jrnl. Sci. 5 361 The rock..shows numerous tabular phenocrysts..and a few anhedra of augite.

1913 G. A. J. Cole Outl. Mineral. ii. 20 The individual crystal in such cases is sometimes said to be anhedral, because it has no good bounding planes, in opposition to the well-crystallised or euhedral forms.

1950 N. H. Hartshorne & A. Stuart Crystals & Polarising Microscope (ed. 2) iii. 44 Crystals which are bounded by plane faces are described as idiomorphic or euhedral, and irregular ones as allotriomorphic or anhedral.

1961 J. Challinor Dict. Geol. 7/2 ‘Anhedral’, ‘euhedral’, and ‘subhedral’, in mineralogy, are probably to be preferred to ‘allotriomorphic’, ‘idiomorphic’, and ‘hypidiomorphic’ as avoiding any confusion between mineralogical terms and petrographical-textural terms.

1896 L. V. Pirsson in Amer. Geologist XVII. 94 Since the term crystal, when strictly used, means a body possessing not only a certain internal molecular structure, with definite physical properties, but more especially an outward symmetrical form with plane faces, it is evident that there is no good term for the rounded or formless masses in which minerals occur in rocks. Therefore, after consultation with Prof. E. S. Dana, the term anhedron (meaning without planes) is proposed for these formless masses which possess the internal structure of crystals; and such minerals may also be spoken of as having an anhedral development.