the world > the earth > minerals > mineral structure or appearance > [adjective] > cleavage or fracture > having cleavage at particular angles (4)
Of a mineral: exhibiting cleavage parallel to the primary plane; designating cleavage of this kind.
Having cleavages at right angles; = orthoclastic, adj.
Chiefly of feldspar: having cleavages at right angles. Cf. orthoclase, n., plagioclastic, adj.
Mineralogy. Having cleavage planes at right angles to one another; = orthoclastic, adj. Obsolete. rare.