Ludlockite on Zincian Siderite


Composition: Pb2+Fe3+4As3+10O22
Crystal System : Cubic
Lustre : Sub-adamantine, earthy
Hardness : 1.5-2.0
Specific Gravity : 4.40
Year of Discovery: 1968
IMA Number: 1969-046
IMA Status: Approved
Discovered By: Frederick Ludlow Smith and Charles Locke Key (American dealers)
Named for: Discoverers
References: Embrey et al. (1977a)


  • Supergene
  • 2nd Oxidation Zone
  • 3rd Oxidation Zone

Notable Finds

The type specimen is from the second oxidation zone; probably 30 Level. A second discovery on 44 Level (third oxidation zone) produced many small specimens of ludlockite, some of which were yellow in colour, and included possible pseudomorphs of ludlockite after chalcocite.