Like labradorite it usually exhibits on the surface of easiest cleavage parallel striations due to twinning structure.
But by far the most important kind of regular conjunction of crystals is that known as “twinning.”
This twinning may be produced by pressure acting either during the crystallization of the rock or at a later period.
In families where twinning is frequent, bodily deformities likewise occur with frequency.
The second method, known as “twinning” or “parting,” avoids this loss and is also more rapid.
The plate of material is rather wider than before, and is formed into two combs simultaneously, by the aid of a twinning machine.
It is of some interest on account of the twinning and the beautiful development of its crystals.
A twinning line, if an intersection edge, should be solid; if not an intersection edge it should be broken into dashes.