Gmelinite-Na with Analcime

Gmelinite-Na with Analcime from Cairns Bay, Flinders, Victoria, Australia, measuring 82 × 70 × 48 mm and weighing 302 grams. A good, solid piece from the Flinders coast, the locality most closely associated with this species in Australia.

Gmelinite-Na is a sodium zeolite, hexagonal in symmetry, that typically forms flat hexagonal plates or short pyramids, and it is named after the German chemist Christian Gmelin. It sits in the same broad structural family as Chabazite, and the two can occur together or even intergrown. At Flinders the zeolites fill gas cavities in olivine basalt flows of the Eocene Older Volcanics, laid down in the Eocene, and Analcime, with its distinctive trapezohedral crystals, is one of the commonest companions.

Cairns Bay is one of four localities in the Flinders area recorded for Gmelinite-Na on Mindat, with Analcime, Natrolite, Chabazite and several other zeolites documented from the same vesicular basalt. Flinders is best known for its large Gmelinite crystals and has long been a reference area for Victorian zeolite collecting, which explains why this species is so well represented among the Flinders pieces from the David Vince Collection.