Spherocrystals

Spherocrystals, or spheroliths, are distinctive aggregates of acicular or fibrous crystals. In these aggregates, the vertices of all constituent individual crystals converge at a single point, which is the center of a sphere. In the case of optically uniaxial constituents, their optical axes are arranged along the radii of the sphere. For biaxial constituents, one of the axes of the triaxial ellipsoid lies along these radii. In both cases, in convergent polarized light with crossed Nicols, in sections perpendicular to the optical axis, a dark cross characteristic of uniaxial crystals is visible. Unlike this case, we observe the movement of the cross when rotating the object on spherocrystals. An example of such formations can be salicin C₁₃H₁₈O₇ (a glycoside of salicyl alcohol), amylose of starch, and other compounds found in plant and animal organisms.