Calcite

specimen number:
2063796

location:
Irai, Rio Grande do Sul, Brazil

description:
Colorless slightly translucent semi lustrous spiky crystals of calcite, the most prominent crystal measuring 7.0 from tip to tip, set on matrix. Bluish green celadonite is present upon the matrix. This is in great condition. Brightly fluorescent. The specimen comes with a previous label from the collection of Ray DeMark.

Irai, situated in the northern part of Rio Grande do Sul, Brazil, is renowned for its extensive basaltic lava flows formed millions of years ago during volcanic episodes associated with the opening of the Atlantic Ocean. Within these massive volcanic layers, trapped gas bubbles eventually became hollow vugs and cavities that allowed silica-rich hydrothermal fluids to crystallize into magnificent amethyst geodes and quartz deposits. Local mining and quarrying operations have thrived in the region since the mid-twentieth century, utilizing open-pit and underground extraction to recover vast quantities of geode material. While amethyst remains the dominant commercial gemstone of the area, miners and mineral collectors frequently discover distinct secondary mineral phases inside these cavities, including well-formed calcite crystals that coat or grow alongside the quartz layers, highly prized by collectors for their varied habit and pristine contrast against dark basaltic matrix.

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