Lamellar twinning is sometimes seen. Cleavage is in four directions all with varying quality with one direction being perfect, two directions being good and one direction being only distinct. All cleavage angles are non-right angles. Fracture is uneven to conchoidal. Streak is white.
Some specimens are fluorescent orange in long-wave UV light.
Best Field Indicators are density, associations, environment, lithium flame test and especially the numerous cleavage angles.