Quartz

specimen number:
2262244

location:
Mamaju, West Sulawesi, Indonesia

description:
A loose cluster of attractive purple botryoidal slightly translucent crystallized quartz. This is in good condition all around. There are no points of attachment.

The Mamuju locality, situated along the coastal region of West Sulawesi Province, Indonesia, is a globally celebrated modern source for a highly distinctive variety of purple botryoidal quartz colloquially known as grape agate or amethyst chalcedony. Geologically, these unique specimens formed within a heavily weathered, Tertiary-age volcanic suite dominated by altered andesitic and dacitic lavas, tuffs, and breccias. During late-stage hydrothermal activity, low-temperature, silica-rich fluids filled vesicular cavities and open fractures within the volcanic rock, precipitating microcrystalline quartz over millions of years as interlocking clusters of tiny, spheres ranging from several millimeters to centimeters in diameter. The vibrant coloration, varying from pale lilac and amethystine purple to deep grape hues, is caused by trace iron and aluminum impurities subjected to natural irradiation, with the surfaces often displaying a glittering, chatoyant drusy coating. Historically, the deposit was discovered relatively recently by local residents, with the first significant specimen extraction and artisanal surface quarrying commencing around 2015. Unlike heavy corporate underground mining operations, the site has been worked almost exclusively as a seasonal, hand-dug excavation by independent local miners who carefully extract the delicate, clay-embedded clusters from shallow pits and hillside trenches.

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