Volkovskite [KCa
The crystals possess perfect {010} and {100} cleavages occurring as thinly layered pseudohexagonal/triangular, elongated platy masses. Volkovskite is biaxial positive, with indices of refraction α 1.539(2), β 1.540(2), and γ 1.605(2); 2V
A crystal structure refinement confirms the basic model of bibr" href="#ref-12">Rastsvetaeva et al. (1992). The crystal structure determination refined to R = 2.1% for 5266 unique reflections. The layered borate structure consists of a double layer of borate sheets parallel to (010). Between the double layers there are two types of cross linkage: Ca polyhedra bond two double layer slabs and K polyhedra bond the double slabs. Many borate minerals found in potash deposits form layered structures, such as biringuccite, nasinite, gowerite, veatchite polytypes, and volkovskite. The volkovskite structure obtained in this study is compared to related layered borates.