Canadian Rockhound: Kukharenkoite-(Ce)

Kukharenkoite-(Ce)
Abstracted by Malcolm Back

Kukharenkoite-(Ce), ideally Ba₂Ce(CO₃)₃F, is a newly described mineral species from the Khibina massif and the Vuorijäryyi massif, Kola peninsula, Russia, from the Poudrette quarry, Mont Saint-Hilaire, Rouville Co., Québec, and from the Demix-Varennes quarry, Saint-Amable sill, Varennes, Verchéres Co., Québec. All of these localities are designated as the type localities as cotype specimens from each were deposited in the Mineralogical Museum, Dept. Of Mineralogy, St-Petersburg University, Russia, and at the Canadian Museum of Nature, Ottawa. The material from Mont Saint-Hilaire was originally designated as UK65. It was found in thin seams in a hornfels xenolith associated with calcite, siderite, cordylite-(Ce), albite, quartz, pyrrhotite, pyrite and rutile.

Kukharenkoite-(Ce) forms small (0.01 - 1.0 mm) prismatic crystals which are often in dendritic, stellate or irregular intergrowths up to 2 - 3 mm across. Rarely the mineral occurs as platy crystals (0.1 - 2 mm) or anhedral grains (0.05 - 0.2 mm). It is colourless or very pale white to silvery grey or pinkish grey, and the streak is white. It is transparent to translucent, with a vitreous to greasy lustre. Cleavage or parting were not observed and it is brittle with an uneven fracture. The Mohs hardness is 4.5, and does not fluoresce in ultraviolet light. The mineral is soluable in HCl with effervescence. The following data were measured on MSH material. Kukharenkoite-(Ce) is biaxial negative, with indices of refraction a 1.594(1) b 1.710(3) and g 1.715(3); 2V_meas. 16(1)°, 2V_calc.22° (for l =590nm). The optical orientation is Y ť b and the dispersion is medium r > v. Kukharenkoite-(Ce) is monoclinic, space group P2₁/m , a 13.418(9) b 5.077(1) c 6.714(2) Å, b 106.56(2)°, V 438.3(4) Å and Z = 2. D_meas.= 4.7(1) g/cm³ (measured on Khibina material) and D_calc.= 4.73 g/cm³ (calculated on MSH data).

Source:

Zaitsev, A.N., Yakovenchuk, V.N., Chao, G.Y., Gault, R.A., Subbotin, V.V., Pakhomosky, Y.A. & Bogdanova, A.N. 1996. Kukharenkoite-(Ce), Ba₂Ce(CO₃)₃F, a new mineral from Kola peninsula, Russia, and Québec, Canada. Eur. J. Mineral. 8:1327-1336.

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