Collector’s Edge Minerals, Inc. has just acquired some fantastic new quartz v. amethyst specimens from the Mamuju Area of West Sulawesi Province, Indonesia. These specimens are well known for their deep, rich purple colors and nice luster. The botryoidal amethyst aggregates look similar to grapes in shape and color and often receive the nickname “grape agate.” However, “agate” is not an entirely correct term here, as most of the crystals have a drusy surface rather than a microcrystalline texture. We land on a better suited name of “quartz v. amethyst” for these specimens, giving the most accurate description to the specimens’ mineralogy.
Locality: the Mamuju Area sits on the western coast of Sulawesi, an island of Indonesia in the West Sulawesi Province indicated in the Map above by the red area. Mindat image.
Map of the Mamuju peninsula showing the locations of the major diggings for “grape agates”. Joel Ivey, The Mineralogical Record vol. 49, 2018 photo.
These “grape agates” first started showing up on the American mineral market in 2016. While the majority of the quartz produced from the area is purple, there are also specimens with other shades including blue-green, grey, and pale brown. Intensity of color in these are inversely related to the diameter of the individual spheres, with the most intense occurring generally in spheres averaging 4mm in diameter.
The botryoidal amethyst is found by miners in the area hosted in small pockets of calcium and magnesium rich blue-green clay. It is likely that the amethyst is formed in the clay, settle down within it, and become loosely attached with time.
Summary of the geology of Sulawesi showing principal structures and geologic features. Red arrow in Western Sulawesi indicates the Manakara mining district, source of “grape agate.” Watkinson (2011) Map modified by Joel Ivey, The Mineralogical Record vol. 49, 2018 photo.
Many of these new Quartz v. Amethyst clusters are available, here on our website . These specimens have keystone prices starting as low as $75.00. All are great additions to any mineral collection, display well from multiple orientations, and are spectacular examples of the mineral species from this locality. Additional information and photos/videos of our finest retail specimens are available by contacting Richard Jackson or Steve Behling at email@example.com.