Grape Agate crystal Mushroom carving

Grape agate is a marketing name for purple aggregates of tiny quartz crystals with a spherical (botryoidal) habit. The name reflects their purple color and how they occur in clusters that resemble bunches of grapes. This material is found in the Mamuju area, near the western coast of Sulawesi, an island of Indonesia.

Andesite lava behaves differently than basalt; it is more viscous due to its mineral makeup, so when it produced pillow formations on Sulawesi, voids were left between individual pillows. It is in these voids that the grape agate eventually formed.