Quartz (SIL-0048)

specimen number:
9273121

location:
Mamaju, West Sulawesi, Indonesia

description:

Attractive glistening purple translucent spherical shaped crystal groupings of quartz measuring to 0.7 cm in diameter across the years crystallized quartz matrix. This is crystallized completely all around and in super condition. Very attractive.

The Mamuju area, located in the West Sulawesi province of Indonesia, is a globally recognized extraction zone for a popular mineral specimen known in the gemstone trade as grape agate, which is scientifically classified as a botryoidal aggregate of crystallized macrocrystalline quartz rather than true banded agate. Geologically, these unique spherical clusters formed during the Miocene epoch within the cavities of intermediate volcanic rocks, specifically trachyte and andesite pillow lavas that rapidly cooled upon contacting seawater. Hydrothermal fluids subsequently dissolved silica from the surrounding volcanic glass, depositing it within the rock voids layer by layer to form radiating, fibrous quartz spherulites embedded in a soft magnesium- and calcium-rich clay matrix. The history of small-scale quarrying and hand-tool extraction in the rugged, jungle-covered mountains around Mamuju began around 2014, when local villagers first discovered weathered float material along streams near Ngalo Beach. Systematic digging into the primary mountain clay pockets expanded rapidly between 2015 and 2016 to meet global collector demand, and localized manual extraction by artisanal miners has continued consistently through the 2020s to supply the international mineral market.

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