Radiating Calcite Crystals - Irai, Rio Grande Do Sul, Brazil

Contributed by: Chris Clemens
Date: Apr 28th, 2026
Locality: Iraí, Rio Grande do Sul, Brazil (See on Mindat)
Size: 32.2 x 21.1 x 38.5 mm

Description:
A radiating cluster of translucent gray-white calcite crystals aesthetically perched on a dark matrix, from Irai, Rio Grande Do Sul, Brazil. As is typical for these calcites from Irai, they show a bright orange, fluorescent response under shortwave and midwave UV, and a dimmer pink/red response under longwave UV.

Originally posted by Chris Clemens on Nature's Rainbows in 2017.

Fluorescence under shortwave UV light.

Fluorescence under midwave UV light.

Fluorescence under longwave UV light.

Normal light.

Summary of luminescence responses:

Calcite (Mindat) (RRUFF)

• Fluorescence under Longwave (365nm LED) UV light: Red
• Fluorescence under Midwave (305nm Lamp/Mercury) UV light: Red
• Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Red