Stilbite with Calcite

This specimen is Stilbite with Calcite from Giblin Street Quarry, Lenah Valley, Hobart, Tasmania, Australia, measuring 61 x 48 x 25 mm and weighing 32 g. It is recorded with the David Vince Collection and the Ruth Coulsell Collection. Stilbite is a zeolite mineral, typically forming sheaf-like or bow-tie clusters of pearly, lustrous crystals within the vesicles and cavities of basaltic rock. Zeolites crystallise from hydrothermal fluids circulating through cooling volcanic rock, and the cavity-filling habit seen here is characteristic of the species. Calcite is a common companion mineral in these basalt-hosted zeolite occurrences, having crystallised from the same mineral-bearing solutions within the same cavity system. At 61 x 48 x 25 mm, the specimen is a compact cabinet piece showing the characteristic Stilbite habit well. Zeolite specimens from Tasmanian basalt localities are valued for the clarity and lustre of their crystal clusters, and this piece carries a double provenance, recorded from both the David Vince Collection and the Ruth Coulsell Collection.