Quartz

specimen number:
2292264

location:
Rio Grande do Sul, Brazil

description:
An interesting crystallized stalactite of quartz. In good condition all around.

The state of Rio Grande do Sul, situated in southernmost Brazil, is an internationally prominent mining region famous for hosting massive economic deposits of quartz varieties, particularly amethyst and agate. Geologically, these minerals are hosted within the Lower Cretaceous age Serra Geral Formation, a colossal continental flood basalt province where cooling lava flows trapped massive volumes of volcanic gas. Over geological time, low-temperature, silica-rich meteoric and hydrothermal waters percolated through the basalt, slowly precipitating microcrystalline chalcedony and macrocrystalline quartz prisms inside the immense vesicular cavities to form large, hollow geodes. Organized, small-scale quarrying and open-pit mining began in the late nineteenth century around the 1870s and 1880s, initially driven by European immigrants who discovered rich surface deposits. Industrialized extraction and underground tunneling intensified through the mid-to-late twentieth century, developing into a major continuous commercial sector centered around municipalities like Ametista do Sul that remains highly active and productive well into the 2020s.

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