Quartz

specimen number:
2292449

location:
Rio Grande do Sul, Brazil

description:
Lustrous purple crystals of quartz across several sides of this matrix. Several of the sides have been cut and polished. Very slight damage present, still in good condition. Nice decorator specimen.

The state of Rio Grande do Sul, Brazil, is known for its extensive deposits of amethyst, which are hosted within the Serra Geral Formation of the Parana Basin. This geological province formed during the Early Cretaceous period, when massive volcanic activity produced thick sequences of basaltic lava flows. As these flows cooled, gas bubbles created large, almond-shaped cavities known as geodes. Over subsequent geological time, hydrothermal fluids rich in silica infiltrated these voids, depositing crystalline quartz that, through natural irradiation and the presence of iron impurities, developed the characteristic purple color of amethyst. Large-scale mining of these geodes, particularly in the Alto Uruguai region, intensified during the twentieth century, turning this area into a primary global source for amethyst specimens. Artisanal and commercial mining methods continue to extract these geodes from the weathered basalt layers, where they are frequently found embedded within the host rock.

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