Krausite in fumaroles from Santa Bárbara mine, northwestern Argentina

MÁRQUEZ-ZAVALÍA, M. F. LOMNICZI DE UPTON I. AND GALLISKI M. A.

NEUES JAHRBUCH FUR MINERALOGIE-ABHANDLUNGEN

Año: 2001 p. 378 - 384

0077-7757

Abstract: Krausite, monoclinic KFe(SO4)2. 1-1 20, has been known so far from onlythree localities. It was now discovered in the Santa Bárbara mine, a sulphur depositlocated in northwestern Argentina, in a new paragenetic environment, formed bycurrent activity of thermal springs. The mineral occurs in a soft sulfate mass depositedaround two fumarolic vents that discharge a CO 2-rich aqueous vapour phase inthe floor of underground works. Associated minerals are hexahydrite, alunogen andvoltaite. Krausite forms rosettes S 1 mm in diameter, composed of short prismaticcrystals of pale lemon-yellow color. Unit-cell parameters are a 7.908(10), b 5.127(5),c 8.951(11) Á, 13 102°, V 354.1(5) Á s . The crystals are transparent with perfect cleavage// to {001}, (+) 2Vca(, = 88°, a = 1.588(3), 13 = 1.645(3), y = 1.714(3). Thechemical analysis gave Na20 0.70, K20 17.36, Fe203 25.91, SO3 50.90, H2O 4.96,total 99.83 wt.%, leading to the formula Ki.i6Na6.o7Fe 02 (SO4)2 . 0.86 H2O.Key words: krausite, thermal springs, fumarolic vents, Argentina.