Jamborite

Crystal System: Hexagonal
Status of Occurrence: Unconfirmed Occurrence
Distribution: Rare
Chemical Composition: Nickel iron hydroxide hydrate
Chemical Formula: Ni(OH,S,O)2.nH2O
Method(s) of Verification: all occurrences - visual verification only.

Chemical Group:

  • Oxides & Hydroxides

Geological Context:

  • Supergene: in situ natural oxidation & weathering deposits
Introduction: the bright green mineral jamborite forms by oxidation of primary nickel-bearing sulphides, such as millerite.
Occurrence in Wales: jamborite has been reported as an alteration product on millerite, in clay ironstone nodules from the Coal Measure strata of the South Wales coalfield. However none of these occurrences has been confirmed by analytical methods. Previous workers recorded this green coating as a mixture of morenosite and an unidentified sulphate (North & Howarth, 1928) or morenosite alone (Firth, 1971). Subsequent X-ray diffraction analysis by the National Museum of Wales (e.g. NMW X-902) has failed to provide a distinct pattern and confirm the identity of either mineral, or of the occurrence of jamborite.

Key Localities:

  • Bedwas Colliery, Caerphilly, South Wales: a Natural History Museum specimen (B.M. 1971, 363) from Bedwas Colliery, Caerphilly, is labelled ?jamborite on millerite, although this has not been confirmed by analytical data.
  • Cymmer Colliery, Porth, South Wales: jamborite has also been found at Cymmer Colliery (R.S.W Braithaite, unpublished data, cited in Bevins, 1994).

References:

  1. Bevins, R.E., 1994. A Mineralogy of Wales National Museum of Wales, Geological Series No. 16, Cardiff, 146pp.
  2. Firth, J.N.M., 1971. The Mineralogy of the South Wales Coalfield. Unpublished Ph.D. thesis, University of Bristol.
  3. North, F.J. & Howarth, W.E., 1928. On the occurrence of millerite and associated minerals in the Coal Measures of South Wales. Proceedings of the South Wales Institute of Engineers, 44, 325-348.