Quartz

specimen number:
1052852

location:
Rio Grande do Sul, Brazil

description:
A matched pair of cut and polished agate, this with a cavity lined with crystallized quartz.

Rio Grande do Sul, the southernmost state of Brazil, is famous for its extensive deposits of agate, which are hosted within the early Cretaceous basaltic lava flows of the Parana Basin, formed roughly 130 million years ago. As the vast basalt flows cooled, escaping volcanic gases left cavities, or vesicles, in the rock. Over millions of years, silica-rich groundwater seeped into these cavities, depositing microscopic quartz crystals layer by layer from the outer walls inward, creating the characteristic banded structures. Historically, mining of these geodes began in the early nineteenth century with German immigrants, who recognized the quality of the material and began shipping it back to the lapidary cutting centers of Idar-Oberstein, Germany. Today, the Salto do Jacui region is the primary extraction hub, supplying large quantities of basalt-hosted agate to global markets for industrial, ornamental, and lapidary use.

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