Natrolite with Analcime

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Interesting locality example for the species, crystals of natrolite measuring to 1.5 cm in size across a matrix with the bottom side mostly covered with analcime crystals. In good condition.The Pahau River in the Canterbury region of New Zealand's South Island originates in the Tekoa Range and flows southward past Culverden toward the Hurunui River, carving through a landscape shaped by ancient Mesozoic greywacke and argillite basement rocks of the Torlesse terrane. As a permanent geographic feature of the region rather than an anthropogenic structure, it has no recorded opening or closing dates. The regional geology features extensive greywacke formations alongside associated igneous intrusions and volcanic rocks, within which localized cavity fillings and secondary mineral deposits occur. Within these volcanic or altered mafic contexts in the wider Canterbury and North Canterbury volcanic systems, zeolite group minerals such as natrolite form as fine radiating crystal aggregates or needle-like growths inside rock vesicles.