Phillipsite

Phillipsite from Boral Quarry, Bundoora, Melbourne, Victoria, Australia, measuring 60 × 38 × 34 mm and weighing 98 grams.

Phillipsite is a zeolite that typically forms in the gas cavities of basaltic rock, where mineral-rich fluids slowly deposit it long after the lava itself has cooled. It's known for complex, often pseudo-octagonal twinned crystals, and material from Bundoora characteristically starts out as clear, glassy crystals that turn white as they dehydrate on exposure to air. The Boral Quarry at Bundoora, within Melbourne's northern suburbs, is one of Victoria's best documented zeolite localities, also producing Natrolite, Thomsonite and Calcite from the same basalt.

This piece comes from the Allan Waldon Collection. Suburban Melbourne basalt quarries like this one are an easy entry point into Victorian zeolite collecting, and a nice way to see how much variety a single basalt flow can produce once you start looking closely at its cavities.