Crocoite with Gibbsite

Crocoite with Gibbsite from Adelaide Mine, Dundas, Tasmania, Australia, measuring 65 × 60 × 35 mm and weighing 48 grams. The supplied association adds another point of interest to a classic Tasmanian mineral locality. Crocoite and Gibbsite belong to very different chemical groups, so the combination invites attention to more than the principal species alone.

Crocoite is lead chromate, while Gibbsite is an aluminium hydroxide. Both can be connected with alteration processes, although the record for this piece does not establish the order in which they formed. Their association offers a compact way to explore the chemical diversity of secondary minerals, bringing lead-and-chromium mineralogy together with an aluminium-bearing species.

Slender orange prisms stand among pale mineral material, producing the strong colour contrast that makes this piece so engaging. The open spaces between the narrow crystals give the cluster a light, intricate appearance. There is plenty to enjoy in the whole specimen, but the individual orange lines and their relationship with the pale surroundings are especially rewarding at closer range. The specimen comes from the Anne McDonald Collection. That provenance adds a named collection to the locality and association, preserving the information that makes an individual piece recognisable within a wider catalogue. It is a rewarding subject for a Tasmanian mineral display: a well-known lead mineral presented with an additional species and a clear collecting connection.