Gmelinite-Na with Analcime

Gmelinite-(Na) with Analcime from Cairns Bay, Flinders, Victoria, Australia, measuring 110 × 81 × 61 mm and weighing 549 grams. A substantial piece of one of the less commonly collected Victorian basalt zeolites.

Gmelinite-(Na) is the sodium-dominant member of the Gmelinite series, a hexagonal zeolite typically forming tabular to barrel-shaped crystals, quite different in habit from the rounded trapezohedral Analcime that often shares its cavities. Both minerals crystallised from the same family of late-stage, silica- and alkali-rich fluids moving through gas cavities in the cooling basalt around Flinders on the Mornington Peninsula, with Gmelinite-(Na) a noticeably less common find at Cairns Bay than the Natrolite collectors more usually bring home from the locality.

A piece of this size naming Gmelinite-(Na) specifically is worth a second look for anyone building a serious Victorian zeolite suite beyond the more commonly available species from the same ground. This piece is from the David Vince Collection.