Image: Andrew Silver (Public domain)
trigonalcommonSulfates
Jarosite
KFe3(SO4)2(OH)6
This specimen displays jarosite as a yellowish-brown, earthy to finely crystalline mass, exhibiting a dull to somewhat vitreous luster.
Jarosite Physical Properties
Mohs Hardness
2.5Crystal System
trigonalLuster
vitreousStreak Color
pale yellow to brownish-yellowCleavage
distinct on {0001}, but rarely observed due to fine grain sizeFracture
uneven to splinterySpecific Gravity
3.16Colors
yellow, yellowish-brown, brown, reddish-brownTransparency
translucent to opaqueType Locality
Common in oxidized sulfide deposits worldwide, including various acid mine drainage sites.Mineral Group
SulfatesUses
indicator mineral for acid sulfate soils and acid mine drainage, minor source of iron, collector's specimenAssociated Minerals
pyrite, goethite, limonite, other iron oxides and hydroxidesRarity
commonGeological Context
Jarosite is a secondary mineral that forms in the oxidized zones of sulfide ore deposits, particularly in acid mine drainage environments, where iron sulfides like pyrite are weathered in the presence of potassium and sulfate.
