Stilbite-Ca

Das Antas Tunnel, Veranopolis, Rio Grande do Sul, Brazil

8×7,5×4 cm. (longest Stilbite 2,5 cm.)

Ex Henry Currier collection specimen n°493. We report in full the description, made by Currier, on the two labels that accompany this specimen :

“Between Veranopolis and Bento Goncalves – a cluster of brownish black stilbite sheaves to about 2 cm with a few small heulandite crystals on a tan matrix. Only one like it I ever saw except for one on Mindat. Got the specimen from Bill Picket”.

For us this specimen speak for itself, perfect synthesis of beauty and rarity.

Stilbite-Ca, a calcium-rich variety of stilbite, is a mineral belonging to the zeolite group.

The Rio Grande do Sul state is known for its rich deposits of zeolites, including Stilbite-Ca, particularly within the Paraná Basin, a large igneous province that extends over Brazil, Paraguay, Argentina, and Uruguay.  This area has a significant geological history tied to the volcanic activity that contributed to the formation of these minerals.

Stilbite-Ca, often formed in amygdaloidal basalt, is commonly found in association with other zeolite minerals like heulandite and chabazite, and can also coexist with quartz, calcite, and other secondary minerals formed in volcanic and metamorphic environments. Stilbite-Ca forms primarily in hydrothermal environments where low-temperature and low-pressure conditions prevail, often crystallizes from fluids rich in aluminum and silicon, typically in basaltic volcanic rocks. The mineral is deposited in cavities and fractures within these rocks, where hydrothermal fluids circulate. For more info    and