Indonesian opal – Cabochon – Indonesia

Indonesian opals are found mainly on the islands of Java and Borneo, with smaller deposits also located on Sumatra. Compared to renowned Australian mining areas, these stones are less widespread. They are most often volcanic in origin, forming where silicate-rich solutions deposit in rock fissures in regions of intense volcanic activity.

Their colors can range from milky white or grayish tones to dark, sometimes nearly black shades. Under the right lighting conditions, some specimens exhibit a subtle rainbow play of colors. So-called “wood opals,” which form when ancient wood becomes permeated and fossilized, are also not uncommon. These often retain visible organic patterns from the original material.

Opal mining in Indonesia is not as extensive as in some other countries, which partly explains the lower global awareness of these stones. Extraction is frequently done by hand, with minimal mechanization, and many specimens are subsequently cut and polished.

Indonesian opals are valued primarily for their exotic origin. They are rarely exported in large quantities, making them a sought-after yet rare addition to collectors’ portfolios.