amethyst - crystal clusters - set of five student specimens from Brazil which continues to operate the

which continues to operate the mine (photo) for lead and zinc

Occasionally the metamorphism produces a pegmatite with large crystals that form when a fluid-rich magma allows rapid movement of atoms

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amethyst - crystal clusters - set of five student specimens from Brazil which continues to operate theAmethyst quartz SiO2 These amethyst crystal clusters formed as linings in gas bubbles in the Parana flood basalts in Rio Grande do Sul province, Brazil. Recent 40Ar 39Ar dating shows these basalts erupted over a roughly 2 million year period beginning 135 1 million years ago. The Parana Etendeka flood basalts cover an extensive area in southern Brazil and parts of Uruguay, Paraguay and Argentina in South America and in Namibia and Angola in