Kassite from the Diamond Jo quarry, Magnet Cove, Hot Spring County, Arkansas: The problem of cafetite and kassite

Small (<0.5 mm), brownish-pink platy rosettes and yellow spherules, in cavities in nepheline syenite at the Diamond Jo quarry, Magnet Cove, Hot Spring County, Arkansas, have been identified as kassite, CaTi₂O₄(OH)₂, a mineral previously known only from the Kola Peninsula, USSR. The Magnet Cove kassite is orthorhombic, in space group Ammm, A2mm, A222, or A2,22, with unit-cell parameters a = 12.10, b = 31.65, c = 4.95 Å, and Z = 16; d_calc = 3.28 g/cm³. Principal X-ray powder lines [d in Å, (I)] are 7.85(10), 3.26(7), 2.565(7), 1.910(8), 1.898(6). The X-ray powder and single-crystal data and density correspond to those reported by earlier workers for cafetite, (Ca,Mg)(Fe,Al)₂Ti₄O₁₂·4H₂O, from Kola, but the chemical and physical properties correspond to those given in their description of kassite. These earlier workers may have intermixed samples during their X-ray study of kassite and cafetite.