What is Walfordite?
Walfordite is a rare iron tellurium oxide, usually dark and fine-grained, formed in unusual tellurium-rich oxidation environments.
Mineralogy and structure
Reference formula: Fe3+Te3O8. Walfordite has a cubic structure related to complex tellurium oxides. COD 9004537 is used as a representative composition because natural Fe-Mg-Ti substitution is documented. Walfordite is classified with oxides and has cubic crystal symmetry. Typical hardness is 5–6 on the Mohs scale and specific gravity is approximately 5.0–5.5.
Colour, lustre and habit
Typical colours include black, brown-black, dark red-brown, grey. The usual granular, massive, crusty habit and sub-metallic, adamantine, dull lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Walfordite forms in or is associated with oxidised tellurium-gold deposits, hydrothermal veins and complex secondary ore assemblages. Important documented localities include the United States, Mexico, Australia and other rare tellurium districts.
Dark tellurium chemistry in an oxidised ore
Walfordite is a niche reference mineral whose appeal is rarity and unusual chemistry. A small authenticated specimen can document a specialised tellurium paragenesis.
Collecting and care
Tellurium-bearing ore: keep enclosed, avoid dust and acids, and do not cut or grind without professional controls.
