(named after K. V. Chevkin [1802–75], chief of staff of the Corps of Mining Engineers in St. Petersburg), also tscheffkinite, a mineral.
Chevkinite, a diorthosilicate with the chemical composition Ce4Ti4O8[Si2O7]2, contains admixtures of Nb, Th, Ca, Sr, and Zr. It crystallizes in the monoclinic system, forming lamellar and tabular crystals. With respect to chemical composition and structure, chevkinite resembles its polymorphic modifications: orthohombic orthochevkinite and monoclinic perrierite. It is often metamict, and the crystal structure is restored after roasting. Chevkinite is pitch black in color and has a hardness of 5.5 on Mohs’ scale and a density of 4,400–4,930 kg/m3. It occurs together with ilmenite, sphene, and zircon in alkali granites, syenites, and granitic and syenite pegmatites.