Gypsum is often lenticular. In the case of mineral grains it is necessary to specify the development of the crystalline forms. Grains are only incompletely bounded by crystal faces. Grains not bounded by crystal faces. Crystalline particles are also characterized by a particular habit.
Roundness is defined as description of the relative sharpness of the particle corners.
Secondary corners are numerous and sharp. Stronly developed faces with somewhat rounded edges and corners. Secondary corners are numerous. Secondary corners are greatly subdued and few. No secondary corners.