Krutovite

Infobox mineral
name = Krutovite
category = Mineral
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formula = nickel (nickel diarsenide , NiAs2₂)
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color = grayish white
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system = Isometric - Diploidal (2/m 3)
twinning =
cleavage = not observed
fracture = Conchoidal
mohs = 5.5
luster = metallic
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birefringence =
pleochroism = None
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density = pelectron=6.42 gm/cc
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Krutovite is a cubic nickel diarsenide with a chemical composition of NiAs2 and a sulfur content of 0.02-0.34 weight percent (Vinogradova, et al., 1977). Krutovite is showed to have the prime elements of nickel and arsenic with insignificant amounts of cobalt, iron, copper, sulfur, and antimony (Vinogradova, et al., 1977).

Geological Occurrence

Krutovite occurs in the Geshiber vein, Svornost shaft, 8th level, in the northwest strike of Jáchymov (Veselovsky, et al., 2003). Jáchymov, is a Czech mineral town positioned at the altitude of 733 meters above sea level in the St. Joachim's valley of the Ore Mountains.The Ore Mountains also known as Krušné hory is composed of two parts: the Precambrian metamorphic rocks and the Lower Paleozoic metamorphic volcano sedimentary sequence (Ondruš, et al., 2003). The surrounding area lies on fault zones where many minerals develop. The Potucky ore district where krutovite was originally found lies on the northern fault zone. Heading south is the Krušné hory fault zone which surrounds the district of the Jáchymov. The western border lays the Central Fault and the eastern border is formed by the Plavno Fault. Veins come from the major fault lines where krutovite is crystallized at moderate temperature in the hydrothermal origin. The veins can be classified into two categories the morning veins striking along the east and west fault zone and the midnight veins striking from north to south (Ondruš, et al., 2003).Krutovite comes from the midnight vein in the Svornmost mine which contains nickel ores as deep as 100 meters in the granite body. The midnight veins are known to exhibit frequent variations in their strike and dip and have an average width of 10-30 cm. (Ondruš, et al., 2003).In addition to nickel being mined here, tons of silver, bismuth, and uranium were also found in the 19th century. Krutovite forms grains up to 0.1 mm in isometric or irregular form and has also been known to intergrowth with nickel skutterudite and sometimes with tennantite. When this occurs the intergrowth is smooth and there is no visible reaction (Spiridonov, et al., 1996).

tructure

Krutovite is from the family of the isometric-dipoloidal system (3bar2m) and is known to have the same structure type of the cubic order of gersdorffite type P213 (Spiridonov, et al., 1996). Krutovite and gersdorffite were formed together by solid solution decomposition and at a temperature of less than 300 degrees Celsius. Together by ullmannite developed isomorphous substitution of sulfur, arsenic, and antimony occurred (Hem, et al., 1997).

Physical Properties

Krutovite is affiliated with the isometric-dipoloidal crytstal system (3bar 2m) and space group Pa3 (Barthelmy, et al., 2005). Krutovite is opaque with the color of grayish white known paler then the color of nickel skutterudite. In reflected light the mineral has a vivid white with a rosy tint. It has a hardness of 5.5 on the Mohs scale and a luster of metallic (Vinogradova, et al., 1977). Vinogradova, et al., 1977 discussed that the cleavage was not observed. Physical properties are not what only distinguish the mineral but the reflection spectrum also plays an important role. Krutovite has high degree of reflectance about 64.0-67.0% higher then known nickel arseniteds and sulfarsenides (Vinogradova, et al., 1977). The spectrum of reflectance that occurs in krutovite has a wave length range of 440-1100 and a minimum of 480-540 nm. The rose tint of the nickel arsenide gives the small increase of reflectance in the violent and red parts of the spectrum (Vinogradova, et al., 1977).

Biographic Sketch

Kruotvite was named in honor of Georgi Alekseyevich Krutov who was a professor of mineralogy of Moscow University in Russia. Krutov graduated at the Geology Prospecting Faculty of the Moscow Mining Academy in 1931 and is a well-known researcher of nickel and cobalt deposits. From 1933 to 1969, Krutov has conducted several programs and studies throughout his years. Some have included the Co-Ni deposits in Ural, Kazakhstan, Co in Dashkesan deposit, Ni in silicate ores in ultrabasical massifs of Southern Ural, Cu-Ni (Co) deposits Norilsk in the Kranoyarsk region and Monchegorsk in Karelia (Veselovsky, et al., 2003). Krutov devised the significant of chlorine in the arrangement of contact-metaomatic deposits, which is found in the deposits of amphiboles, scapolite, and apatite chlorine. One of Krutov’s great achievements is a monograph called Ore deposits of cobalt that included cobalt and nickel ores in Krusnehory Mts. which was published in 1959 near his hometown in Moscow, Russia (Veselovsky, et al., 2003). Georgi Alekseyevich Krutov lived from April 24, 1902 to December 11, 1989 and contributed a large extent of his life to the mineralogy community which led to the naming of krutovite.

References

*Bayliss, P.; Stephenson, N.C. (1967). The Structure of gersdorffite. Mineralogical Magazine, pp. 38-41
* [http://www.webmineral.com/data/Dawsonite.shtml]
* Hem, Skage R.; Makovicky,Emil. (2004). The system Fe-Co-Ni-As-S; II, Phase relations in the (Fe,CO,Ni)As (sub 1.5) S (sub 0.5) section at 650 degrees and 500 degrees C.Canadian Mineralogist, Vol. 42, Part 1, pp. 63-86.
* Ondruš, P ;Veselovský, F.; Gabašová, A.; Hloušek, J. ;Šrein, V. (2003). Geology and hydrothermal vein system of the Jáchymov (Joachimsthal) ore district. Journal of the Czech Geological Society, Vol.48, Issue 3-4, pp3-18.
* Spiridonov, E. M.; Chvileva, T. N. (1996).The boundary between gersdorffite NiAsS and krutovite NiAs. Transactions Doklady of the Russian Academy of Sciences. Earth Science Sections, Vol. 344, Issue 7, pp. 119-123.
* Veselovsky, Frantisek; Ondrus, Petr; Gabasova, Ananda; Hlousek, Jan; Vlasimsky, Pavel. (2003). History of discovery and study of new primary minerals at Jachymov.Journal of the Czech Geological Society, Vol. 48, Issue 3-4, pp. 207-208.
* Veselovský F.; Ondruš P; Gabašová A.; Hloušek J.; Vlašimský P,.;Chernyshev IV. (2003).Who was who in Jáchymov mineralogy II.: Journal of the Czech Geological Society, Vol 48, Issue 3-4, pp.193 – 205
* Vinogradova, R. A.; Rudashevskiy, N. S.; Bud'ko, I. A.; Bochek, L. I.; Kaspar, P.; Padera, K. (1977). Krutovite, a new cubic nickel diarsenide. International Geology Review, Vol. 19, Issue 2, pp. 232-244