Grape Agate is a relatively new stone to the world, having been recently discovered a few years ago along the beaches of Manakarra, Indonesia. The local people first found small pieces on the beach, and then followed the trail up into the coastal mountains to where the agate formed, and then weathered down from the steep forested hillsides, where it is now mined commercially.
Grape Agate is a chalcedony (a cryptocrystalline form of silica) characterized by small botryoidal, or spherical radiating balls, resembling bunches of grapes. Botryoidal minerals ordinarily form when many tiny specks of sand or other particles are encapsulated over time by layers of mineral deposits that build up radially around the nuclei. As more material is deposited, the spheres grow larger and eventually overlap with those that are nearby and are then fused together to form the botryoidal cluster. Grape Agate is unusual in that it is formed by an uncommon process of the C-axis twisting during rapid growth of the fibrous chalcedony creating a radial structure around a nucleus. Grape Agate is colored by iron and chlorite plus small amounts of other trace minerals such as potassium, aluminum, calcium, and magnesium, that give it it’s deep purple and green hues. Some Grape Agate is coated with a surface layer of fine, sparkling druzy quartz crystals, giving it a silky, almost fuzzy appearance that is highly regarded and sought after.