Natrolite with Analcime

Natrolite with Analcime from Cairns Bay, Flinders, Victoria, Australia, measuring 69 × 66 × 32 mm and weighing 180 grams. A broad, flattish specimen with a good spread of both zeolites across its face.

This pairing of radiating white Natrolite needles against the more rounded, glassy Analcime crystals is one of the signature combinations collectors look for from the Flinders basalts, and it is well documented in the literature on Victorian zeolite localities that Mineralogical Society of Victoria members have built up over the years. Mineralogically, Natrolite and Analcime are both products of the same late-stage, low-temperature mineralising fluids moving through the basalt's gas cavities, but their different crystal systems, orthorhombic needles against cubic trapezohedra, make them easy to tell apart even in the one piece.

Cairns Bay has been worked by collectors on and off for decades, and specimens of this quality, at this size, are becoming harder to source as the more accessible exposures are picked over. This one is from the David Vince Collection, and at a good, broad 180 grams it displays well as a stand-alone piece rather than needing to be paired with others to make an impression.