Calcite from Iraí, Brazil – Large Crystals with UV Fluorescence

This Calcite specimen from Iraí in Rio Grande do Sul, Brazil shows several large pale yellow to cream-colored Calcite crystals on a greenish matrix. Particularly striking is the variation in crystal form: alongside large, clearly flattened to thick-tabular crystals, numerous smaller crystals occur, some of which show cannon-spar-like pointed terminations.

Measuring 7.5 × 5.0 × 4.5 cm and weighing 167 g, this is a cabinet specimen. The crystals are arranged three-dimensionally across the matrix and form an attractive group with several clearly visible individual crystals.

Flattened Calcite crystals with pointed terminations

The larger Calcite crystals are predominantly elongated, flattened to thick-tabular. Numerous smaller, more compact crystals occur between them. Some of these smaller crystals show distinctive pointed terminations formed by three faces, giving them a cannon-spar-like appearance.

The crystals are predominantly translucent. Light can enter and partly pass through the crystals, although they do not appear clearly transparent. Their pale yellow to cream coloration contrasts strongly with the greenish matrix.

UV fluorescence

Under UV light, the Calcite shows clearly visible fluorescence. This gives the specimen an additional mineralogical feature and also makes it interesting for collectors of fluorescent minerals.

The fluorescence is documented in one of the product images.

Calcite from Iraí, Brazil

The area around Iraí in the Brazilian state of Rio Grande do Sul is known for mineral formation in basaltic rocks. Cavities and fractures within the volcanic rock provided space for later mineral deposition, including Calcite.

On this specimen, the basaltic host rock is especially visible on the reverse. The combination of pale Calcite crystals, darker matrix and UV fluorescence makes the piece both mineralogically and visually interesting.