What is Vaterite?
Vaterite is a metastable polymorph of calcium carbonate, usually occurring as fine aggregates, spheres or coatings rather than large transparent crystals.
Mineralogy and structure
Reference formula: CaCO3. Vaterite shares the formula CaCO3 with calcite and aragonite but has a different structure and is less stable. COD 9007475 provides a suitable hexagonal representative model; do not treat it as a calcite duplicate. Vaterite is classified with carbonates and has hexagonal crystal symmetry. Typical hardness is 3–4 on the Mohs scale and specific gravity is approximately 2.5–2.9.
Colour, lustre and habit
Typical colours include colourless, white, cream, yellowish. The usual spherulitic, botryoidal, granular habit and vitreous, pearly, dull lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Vaterite forms in or is associated with caves, springs, biological environments, evaporitic settings and low-temperature carbonate precipitation. Important documented localities include Austria, Germany, Italy, Mexico, the United States and documented biological and cave occurrences worldwide.
The overlooked polymorph of calcium carbonate
Vaterite is attractive to collectors and science-minded buyers because a familiar formula hides a distinct and metastable structure. Form, origin and proof of natural occurrence are central to its value.
Collecting and care
Protect from acids, abrasion and prolonged moisture. Clean gently and record whether the sample is natural, biomineralised or laboratory-grown.
