What is Zirkelite?
Zirkelite is a rare dense zirconium-titanium oxide of alkaline rocks, usually appearing as dark grains enriched in calcium, rare earths and radioactive elements.
Mineralogy and structure
Reference formula: (Ca,Th,Ce)ZrTi2O7. Zirkelite has variable natural chemistry and is represented here by a cubic natural COD model. It is closely related in chemistry to zirconolite, but it is kept as its own mineral record and not collapsed into a duplicate. Zirkelite is classified with oxides and has cubic crystal symmetry. Typical hardness is 5–6 on the Mohs scale and specific gravity is approximately 4.7–5.2.
Colour, lustre and habit
Typical colours include black, brown, reddish brown. The usual granular, massive, disseminated habit and adamantine, sub-metallic, dull lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Zirkelite forms in or is associated with alkaline complexes, carbonatites and late magmatic accessory-mineral assemblages. Important documented localities include Brazil, Russia, Canada, Norway and other zirconium-rich alkaline complexes.
Rare-earth and zirconium chemistry in a black grain
Zirkelite is for the collector who values an unusual geological system: a small black grain from an alkaline complex can carry more chemical information than a much larger ordinary rock.
Collecting and care
May contain uranium or thorium: minimise dust, do not grind, and use appropriate radiation controls for concentrated material. Protect brittle grains from impact.
