Original description: unknown.
Type locality: unknown.
Type material: unknown.
Etymology: from the Greek word σφαλεροζ (sphaleros) meaning treacherous; the mineral sometimes being mistaken for galena, but yielding no lead.
Distribution: оnly a few localities for the finest crystallised examples can be given. Canada: Yukon Territory, Watson Lake; Czech Republic: at Horní Slavkov (Schlaggenwald); England: Cumbria, from Alston Moor; Germany: from Freiberg, Saxony, and Neudorf, Harz Mountains; Mexico: from Santa Eulalia and Naica, Chihuahua, and Cananea, Sonora; Peru: Huaron, Casapalca, and Huancavelica; Romania: Rodna; Russia: Primorsky Krai, Dalnegorsk; Spain: Cantabria [Santander] Province, Picos de Europa Mts, Aliva mine; Switzerland: Valais, Binntal, Lengenbach quarry; USA: Kansas, Cherokee Co., near Baxter Springs; Missouri, Jasper Co., Joplin; Oklahoma, Ottawa Co., Picher; Tennessee, Smith Co., near Carthage, Elmwood mine; Colorado, Eagle Co., Gilman district, Eagle mine (
Anthony et al., 2001—2005). In Bulgaria from Smolyan District, Madan region.
Crystal data
Crystallography: isometric — hextetrahedral.
Crystal habit: crystals tetrahedral, dodecahedral, typically complex and distorted, curved and conical faces common, to 30 cm; also fibrous, botryoidal, stalactitic, cleavable, coarse to fine granular, massive.
Twinning: twin axis [111], twin plane {111}, simple contact twins or complex lamellar forms (
Anthony et al., 2001—2005).
Optical properties
Colour: highly variable, ranging from colourless to dark brown, grey, black; commonly brown, yellow, red, green (
Anthony et al., 2001—2005).
Diaphaneity: transparent to translucent, opaque when iron-rich (
Anthony et al., 2001—2005).
Lustre: resinous to adamantine (
Anthony et al., 2001—2005).
Refractive index: 2.368—2.371 — isotropic (
Lazzarelli, 2012).
Dispersion: very strong; 0.156 (
Arem, 1987: 176); nearly four times that of
diamond.
Pleochroism: none.
