Mineral Database (Saesneg yn unig)

Mineral Database (Saesneg yn unig)
Mineralogy of Wales

Vanadinite

Crystal System: Hexagonal
Formula: Pb5(VO4)3Cl
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Lead vanadate chloride
Method(s) of Verification: Ty-coch - reflected light microscopy & chemical analyses (Criddle & Symes, 1977); Dolgellau Gold-Belt - unrecorded
Geological Context:
  • Supergene : in situ natural oxidation & weathering deposits
Introduction:

vanadinite is a member of the apatite group, and is similar in appearance to pyromorphite and mimetite. It occurs typically in the oxidized zone of lead-bearing mineral deposits. Fine crystallized specimens are known from many mines in Arizona, U.S.A and recently from Morocco.

Occurrence in Wales:

there are very few records of vanadinite from Wales, largely due to the scarcity of vanadium in Welsh ore deposits. Criddle & Symes (1977), produced the only detailed account of vanadinite from the principality, describing the unusual mineralogy of Ty-coch manganese mine in South Wales. Later, in 1994, Bevins noted a specimen of vanadinite from ‘near Dolgelly’ in the NHM mineral collections. Unfortunately no more accurate provenance can be made than that it is likely to have been collected from one of the gold mines in the Dolgellau Gold-Belt given, the association with native gold.

Key Localities:
  • Dolgellau Gold-belt, Gwynedd: Bevins (1994) records that small brown hexagonal prisms of vanadinite occur associated with gold on NHM specimen no. B.M. 67960, labelled as from 'mines near Dolgelly'.
  • Ty-coch, near Porthcawl, South Wales: Criddle & Symes (1977) describe five types of ore material from Ty-coch. Vanadinite is recorded from three of these, each occurring in a different habit: vanadinite and pyrobelonite and intergrowths of the two are minor constituents of a massive, fine grained, compact, very hard, dark grey manganese ore with abundant lenticular masses of varicoloured calcite and barite. Vanadinite within this ore is typically pale lemon yellow, brittle and with no detectable cleavage; grey, somewhat greasy looking vanadinite fills small (5 mm) cavities within massive psilomelane with wad, infilling cavities and replacing limestone; ‘breccia ore’ consisting of goethite, minor hematite, quartz, and limestone fragments occasionally has small encrustations of bright yellow, powdery vanadinite.
References:
  • Bevins, R.E., 1994 A Mineralogy of Wales  National Museum of Wales, Geological Series No. 16, Cardiff, 146pp.
  • Criddle, A.J., & Symes, R.F., 1977 Mineralization at Ty-coch, Glamorgan (Mid Glamorgan), Wales: the second occurrence of pyrobelonite. 

    Mineralogical Magazine, 41, 85-90.