Fluorescent Calcite from Iraí, Brazil

This calcite specimen comes from Iraí in the Brazilian state of Rio Grande do Sul. Several colorless to white calcite crystals sit on a dark basaltic matrix.

The crystals show a clearly developed scalenohedral habit and reach lengths of up to approximately 2 cm. They are intergrown into a three-dimensional group and display well-defined crystal faces. Depending on the lighting, the surfaces show a distinct vitreous luster.

Measuring 4.5 × 4.3 × 3.0 cm, the piece belongs to the miniature specimen size category. The stated weight of 31.8 g includes the plastic display base.

Fluorescent Calcite from Iraí

Iraí is one of Brazil’s well-known source regions for calcite from basaltic cavities. The locality is particularly known for scalenohedral calcite crystals and radially arranged crystal groups.

The crystals formed within cavities in volcanic rocks. Mineral-bearing fluids circulated through these open spaces and deposited calcium carbonate on the cavity walls.

Under long-wave UV light, the calcite shows a pink fluorescence. Depending on the excitation wavelength, calcite from Iraí may also show orange to reddish fluorescence.

The scalenohedral crystal form, dark matrix, and UV fluorescence make this piece a characteristic calcite specimen from Iraí.