Chevkinite

chevkinite

[′chef·kə‚nīt]
(mineralogy)
(Fe,Ca)(Ce,La)2(Si,Ti)2O8 A mineral consisting of silicotitanate of iron, calcium, and rare-earth elements.

Chevkinite

 

(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.

References in periodicals archive ?
These elements are primarily hosted in minerals like apatite, monazite, chevkinite which are found in alkaline rocks including alkali granites and carbonatites, in major.
Ample, brilliantly lighted display cases of different configurations showed off aquamarine, spessartine, elbaite and kunzite gem crystals, mostly enormous, as well as exotica such as the world's biggest crystal of viitaniemiite (17 cm long, and quite sharp), and monster crystals and crystal clusters of rarities like pollucite, beryllonite, and chevkinite. The reigning monarch was a breathtaking, translucent pink, compound crystal of elbaite, 35 cm tall, called the "Rose of Asia," from Paprok, Afghanistan--this piece belongs to a private collector but was brought to Munich courtesy of the Museo di Storia Naturale, Milano.
Next was Umberto Righi's Les Pierres en Fleur (23 rue Didier "Collonge," 38080 l'Isle d'Abeau, France); he still had some of the rare chevkinite from Pakistan among perhaps 6 meters of space filled with individual specimens mostly from China and the Congo.
I saw fewer of these in Denver than I had expected to, but three crystal groups held by Andreas Weerth might attain the size record: the brownish black chevkinite crystals are heavy blades to 6 cm across, most of them dull-lustered but a few very glossy.
Another French dealership, Collonge, had a display case devoted to a new find from Chipral, Pakistan: chevkinite, a black rare-earth silicate mineral, in spectacular, individual thick-tabular crystals to 2.5 x 7.5 cm.
Dudley also had ten giant loose crystals of chevkinite-Ce from above Arondu, Haramosh Range, Baltistan, Pakistan: these are loose, incomplete, black, lustrous wedge-shaped crystals to 3 x 3.5 cm, chevkinite being a species formerly known only in microcrystals.
Melanocerite, ortholavenite, loparite, thorite, thorianite, eudialyte, perrierite, chevkinite, zircon, leucophanite, catapleiite, astrophyllite, tainiolite, calcium-rich seidozerite are found in nepheline-albite phenites at the exocontact.
The very sharp, bladed, wedge-terminated crystals of this complex silicate of Fe, Mg, Ti and the rare-earth elements reach many centimeters long, and occur in heavy groups of jet-black color and almost metallic luster, putting to shame all earlier known chevkinites from localities in Norway and Russia.