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Fossilized Insect Discovered Not in Amber, But in Opal

fossilized insect in opal

A precious opal discovered on the island of Java in Indonesia includes what appears to be a complete insect encased inside. The initial theory is that the encasement may mean the opal itself is opalized amber. (Photo credit: Brian Berger)

By Brian Berger

Last year, I purchased a precious opal discovered on the island of Java in Indonesia. The specimen is an extremely rare example featuring “play of color” throughout the stone. But, most exciting in this particular opal—and likely of most interest to readers of this blog—is not the play of color but rather the inclusion. Embedded within the opal is an intact encased insect.

As evidenced in the photos, you can see what appears to be a complete insect encased beautifully inside. Upon close inspection, the insect appears to have an open mouth and to be very well preserved, with even fibrous structures extending from the appendages.

Further research is being conducted on the specimen currently. The initial theory is that this encasement may mean the opal itself is opalized amber. Theoretically speaking, the insect likely was trapped in tree sap or resin which, over time and under the right circumstances, was preserved as amber with the insect encasement. This is a process many of us are familiar with. However, a second, much rarer process of opalization can also occur. And so, in this case, as conditions changed for the amber specimen, it is possible the amber opalized, preserving the inclusion. Amazingly, the silica surrounding the insect also structurally changed to produce the play of color.

fossilized insect in opal

A precious opal discovered on the island of Java in Indonesia includes what appears to be a complete insect encased inside. While insects encased in amber are well-known, a second, much rarer, process of opalization can also occur while still preserving the insect inclusion, which is believed to be the provenance of this specimen. (Photo credit: Brian Berger)

The specimen was examined recently by the Gemological Institute of America and received a letter of provenance for the rarity of such an inclusion. The letter includes the GIA report number from the examination of the stone. From a gemological standpoint, this is truly an exciting and extremely rare, notable find. And the same can likely be said from the entomological perspective. In the future, I would be eager to collaborate with an expert in insect fossils to investigate the insect inclusion further.

Brian Berger is a GIA Graduate Gemologist and CEO of Timberbrook Capital LLC in Philadelphia, Pennsylvania. Email: fppmdiamonds@gmail.com

17 Comments »

  1. Taking the location of the discovery-tropical. May I suggest that the amber formed in a bamboo stalk as has been know to happen. I have seen examples of suck opal in the past. Are there any thoughts on this?

  2. Much Ethiopian rough opal makes it to Indonesia to be cut. Welo opal often shows this yellow base color,and also shows fibrous plant root inclusions. Very possible this is welo opal with an insect possibly inclusion formed in a similar way (no amber involved or required).

    • this is, and has been identified by GIA as an indonesian specimen; though the amber is just initial theory and the theory may not be correct. Origin has been confirmed

  3. I don’t understand why this is such a mystery. Amber isn’t necessary. Opal is formed by water that is rich in silicon dioxide filling a void. The water evaporates leaving the silica, which is opal. If the water filled the hole with the insect immediately, it would be an anaerobic environment (no air) so it wouldn’t decay.

  4. Is it rare coz opal is formed at hight temperature?..Insect could n t be preserved, that s is why they introduce the ambar therory…Rigth?

  5. The temperature range of formation of opals is actually unknown. Some opals clearly were not (or only very slightly) metamorphosed; some were strongly metamorphosed. Most (but not all!) insect remains are found in amber, which is probably why amber was invoked as an intermediary. A fossil insect collecting site exists in an ancient lake bed about 60 or so miles SW of Denver: insect fossils are found there in both sediments and in amber. Other fossils include the occasional fish and the rare lizard, etc. The site is most famous for its petrified wood: some huge trees were fossilized essentially intact, because of an ancient volcanic eruption.

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