Mineral Database

Mineral Database
Mineralogy of Wales

Tangeite

Crystal System: Orthorhombic
Formula: CaCu(VO4)(OH)
Status of Occurrence: Unconfirmed Occurrence
Distribution: Rare
Chemical Composition: Basic calcium copper vanadate
Method(s) of Verification: unknown
Chemical Group:
  • Vanadates
Geological Context:
  • Supergene : in situ natural oxidation & weathering deposits
Introduction: tangëite is a rare supergene mineral, chiefly found in areas where hypogene copper minerals have been oxidised in the presence of vanadium. The name is synonymous with calciovolborthite. Opinions differ as to which is the preferred name, and even whether either are a valid mineral species.
Occurrence in Wales: the only record of tangëite from Wales is a single specimen in the private collection of C. Hedegaard of Denmark. It is labelled as being calciovolborthite with quartz and chalcocite.
Key Localities:
  • Penrhyn Quarry, Bethesda, Gwynedd: 'Bethesda Slate Quarry': this is presumably Penrhyn Quarry near Bethesda. Chalcocite and chrysocolla, with minor malachite, occur here in fractures within boudinaged basalt dykes which have intruded the mudstones prior to their deformation and metamorphism into slate. Some fine chrysocolla specimens were collected in 1997 (Bevins & Mason, 1998). Anyone with sample suites from this locality is encouraged to recheck them for possible vanadates. Tangëite is yellowish-green with a vitreous lustre.
References:
  • Bevins, R.E. & Mason, J.S., 1998 Welsh Metallophyte and metallogenic evaluation project: Results of a Minesite Survey of Gwynedd.  National Museums of Wales, Cardiff.