Angastonite with Minyulite

Angastonite with Minyulite from Tom's Phosphate Quarry, Kapunda, South Australia, Australia, measuring 53 × 45 × 32 mm and weighing 40 grams. This South Australian phosphate association has the added interest of a named field collector. Together, the quarry locality and the associated minerals give the piece a focused place in a collection of Australian phosphates.

Angastonite is a hydrated calcium, magnesium and aluminium phosphate. Research published in 2022 redefined it as an amorphous mineral, meaning it lacks the long-range atomic order of a crystal. That gives it an unusual place in a phosphate collection and is a useful reminder that mineralogical study can change our understanding of material already held in older collections.

White, finely granular material coats parts of the brown matrix, producing a clear contrast in the overall view. The piece lends itself to close examination of the coated areas and their margins. Its interest is in the small-scale phosphate assemblage and the locality connection, rather than in the outline of a large individual crystal. Vince Peisley is recorded as the collector, and the specimen is associated with the Jon Mommers Collection. Those names preserve a direct human connection with the material. They are particularly useful for a specialist phosphate collection, where field associations and historic identifications often accompany specimens whose full mineralogical story benefits from close study.