Ludlockite

Ludlockite


Composition: Pb2+Fe3+4As3+10O22
Crystal System : Cubic
Colours: Red-brown, orange, orange-brown, copper-red
Lustre : Sub-adamantine, earthy
Hardness (H) : 1.5-2.0
Specific Gravity (S.G) : 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)

Tsumeb is the Type Locality

Distribution

Rare. Second and third oxidation zones.

Occurrence

  • 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.

Paragenetic and General Notes

The type assemblage comprises ludlockite with zincian siderite and quartz, on a tennantite-chalcocite-germanite-pyrite-bornite matrix.

The 44 Level paragenesis is quite different, with ludlockite associated with leiteite, reinerite, stolzite, and schneiderhöhnite (Gebhard, 1999). Other minerals with which ludlockite is associated include germanite; renierite; stottite and stibioclaudetite.

It is notable that the chemical formula of ludlockite was originally presented as (Fe2+,Pb)As5+2O6  (Embrey et al,. 1977a).  However, Cooper and Hawthorne (1996) showed that the arsenic occurs in its intermediate As(III) oxidation state, and that the iron occurs as Fe3+.  The correct formula is therefore Pb2+Fe3+4As3+10O22

Ludlockite has been reported to form pseudomorphs after the following minerals: chalcocite (rare).