'Grape' Amethyst from Sulawesi
An edited article I wrote in MAY 2018, published in the British Micromount Society Newsletter; MK Geological Society Newsletter and in the USA.
Produced with permission and the enormous help from the field geologist in Sulawesi, Joel Ivey. ~ Colleen Thomson ~
This amazing stuff has only recently (in the last year or so), become well known. It was discovered a few years ago (2014) in West Sulawesi, (Sulawesi Barat) in the Mamaju region of the island. (indicated on map below just south of the black arrow) Sulawesi is one of many islands that make up Indonesia.
The Chalcedony (Amethyst) was first discovered as small individual purple balls in the sand on the coast, at the mouth of a river. Larger pieces were found further upstream until it was traced to its source. It is now trench mined extensively in the northern agricultural areas and in the heavily forested areas in the south of the region.
Up until April of 2016 the Sumatran authorities banned all exportation of this material, (and again in October of 2017, but relented a month later with stricter export procedures).
The material is found in very remote areas in the jungle and jagged mountainous terrain that is treacherous at best and in the rainy season, absolutely deadly. One of the miners that I deal with, sadly lost his life, swept away by flood waters cascading down the mountain near the mine.
Sometimes referred to as ‘Batu Manakarra’ or Manakarra Stone– it has been mistakenly attributed to the Manakarra Beach area as its locality, A common deception by local stone dealers to lead competition astray!
Many of the earlier localities in the easier to reach places, particularly low lying farmland, are now finished and the miners must trek dozens of kilometres hacking their way through the dense forests on perilously steep inclines to reach the volcanic outcrops where the Chalcedony/ Amethyst may be found.
The terrain in this region consists of rugged heavily forested mountains over 500m high and with deep very steep sided valleys.
The digging fields are scattered in the steepest most central part of this inhospitable region.
This entire mountain range consists of a Miocene age volcanic unit dominated by mafic lavas, volcanic breccias and tuffs.
The miners dig next to the pillow lava and find traces of a blue clay (probably the result of decomposing host rock) which is indicative of where the Chalcedony/quartz is found. Most of the crystallised material is coated in this blue clay in pockets beside the pillow lava.
The clay is washed off using pressure washers back in the villages and towns where only then can the quality and colour be seen. The miners have learnt to collect the better-quality material to get a better price. Even so, many workings are now abandoned and many more have been unproductive and ‘dry’.
The Amethyst is hard won under dangerous conditions in a remote and inhospitable environment.
Then they must get them down the mountains!
For a more in depth and technical explanation on how the Amethyst may have formed, please read Joel's online article on his website.* But the Basic principal in brief is that pillow lava cools slowly forming volcanic glass and on the edges brecciated masses that leach hydrothermal liquids that lead to decomposition (forming the blue clay) - various other chemicals present (predominantly silica) form the chalcedony/ Amethyst ‘balls’ which rain down on a chalcedony/quartz base (often found as flat areas on these masses) and loosely adhere to each other. Many are found free floating in the clay pockets.
No wonder these marvellous colourful crystal sphere clusters are so sought after!
I am so lucky to have been approached by one of the miners back in 2016 and able to purchase good quality material then. Yes, some remain languishing in my private collection, however I have let some go over the intervening years. Its worth keeping an eye out for additions to the ASIA PAGE.
UPDATE 2026
Research by mineralogists (including Dr. George Rossman at Caltech) confirms the material consists of spheroidal, radially grown quartz/amethyst fibres rather than chalcedony banding characteristic of true agate, backing up the research already done by the world renowned quartz expert Terry Moxon, shown above and carried out in 2017.
NOTE: this amazing material is becoming more scarce as sources run out. The majority of mines are closed and over fifty percent of material is unsaleable. Better quality and colour is only about 20% of the mined material, with very occasional green or blue colours.
Lesser quality dull material is more readily available without the sparkle or vibrancy of previous colours. Please also be aware that there are fakes on sale with dyed spheres- even plastic!
see Joels article here:
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