Cerussite

Cerussite from Brown's Prospect, Rum Jungle, Northern Territory, Australia, measuring 56 × 43 × 32 mm and weighing 144 grams. The open interlocking group gives this lead carbonate a particularly engaging structure to examine. That makes it a useful piece for exploring the range of secondary mineral identities attached to one occurrence.

Cerussite is lead carbonate and is characteristic of the altered parts of lead-bearing deposits. It differs chemically from lead phosphates such as Pyromorphite, even though both can belong to secondary lead-mineral assemblages. A comparison between separately labelled specimens helps show how the same metal can be incorporated into different minerals as the surrounding chemical conditions vary.

Pale cream to white elongated crystals interlock into an open lattice, with brown matrix visible through the gaps. The spaces are as important to the appearance as the crystals themselves, making it possible to follow individual blades through the group. A supported, slightly raised display angle brings out that open structure and the depth within the cluster. Minor Malachite staining along one edge is also recorded with the specimen. This specimen comes from the David Vince Collection and was collected in 1975. The date gives this particular Cerussite a welcome connection with an earlier period of collecting at Rum Jungle. Together with the Brown's Prospect attribution, it provides a historical setting for the open crystal group, making the piece rewarding both as a study of crystal form and as a dated Australian locality specimen.