The objective of this article is to introduce to the on-line community the wonderful range of agate in Indonesia. Although there are many wonderful earth-mined agate gems, there are also a lot of of treated gems that appear to look like the natural ones. I was inspired to write this article by numerous questions I have received from my buyers. This article will highlight the various known treatments so that on-line buyers are more aware and informed to do their purchase intelligently.
Here is a photo of a typical gem store in Indonesia. Prices of Agate range from a low quality piece for a few dollars to a very high quality piece which can cost you several thousands! A friend of mine recently sold a gold pendant with a picture agate of “Jesus Cruzified on a Cross” for US$20,000! So it is pretty much a Willing Buyer Willing Seller Scenario.
Basically, there are a very wide variety of agates. I have divided them into the following category for further elaboration.
1) Dendritic Agate
2) Picture Agate
3) Enhydro Agate
4) Agatized fossil (Coral, Sea Shell etc..)
5) Agate with Mineral Inclusion (Pyrite, Copper, Moss, Rutile, fossil etc..)
Dendritic Agate with it’s tree like, fern shapes and branches is a very interesting and pleasing gemstone.They are really inorganic manganese oxide, typically known as dendtrite.
There is no known treatment on this kind of agate. However, Dendritic agate can be determined by its age. A “young” dendritic agate typically shows dendrite growth that is less defined and the color is lighter in tone. A typical example of it as below.
An “old” dendritic agate has much more defined dedrite growth patterns and darker in tone and some really show spectacular display! A good piece of dendritic agate is as below.
Some dendritic growth can also create a picture effect. Like the above example, a “Maple tree” picture effect is created.
Picture Agate is caused by impurities deposited along cracks of the stone. The impurities form patterns which eventually form a picture effect. Each picture agate is unique in its own right! There are 2 known treatments done.
1) Carbon infusion :- Carbon was injected into the agate to make the picture effect more defined or out-right “creating” the picture effect per say. Below is an example of a picture agate that had been injected with carbon to create a picture effect of “Arabic Word Allah”.
As you can see, you can have a bunch of them as above. Luckily, they are quite easily to detect. A trained eye will be able to see the difference between a natural one from a treated piece.
Below is an example of a natural piece with Arabic Word “Allah” picture effect. Natural ones are scarce and not easily available.
Below is a very fine example of Natural Picture Agate. Bearing a well-defined picture effect of a “Spider”.
2) Inserting a foreign object
It is pretty much like a doublet effect. A foreign object is inserted into the agate and sealed off with glue. This treatment is relatively easy to detect as there will be “breakage” at the edge of the stone like a doublet. Below is an example of a picture agate with foreign object insertion.
It looks perfectly normal from the front but you can see the sealed edge from the above picture.
Enhydro Agate consists of fluid inclusion within a cavity in the agate. You will see a fluid bubble or in some rare cases, a few fluid bubbles within the cavity. It is commonly called “Water Agate” in the trade. This fluid inclusions are millions of years old and usually very pure. Known treatment on the enhydro agate is “water injection”. Agates with a dry internal cavity are selected and a minute hole drilled through to the cavity and water is injected in and then sealed off with glue. You can usually detect this treatment by observing for sealed minute holes. However, this takes some skills to detect.
Extra care for enhydro agate:- Take note that the best way to store enhydro agate is to keep them in water. As agate is a rather porous material, even natural enhydro agate can lose their fluid inclusion under high temperature environment.
Common fossils that had been agatized are Agatized Coral, Agatized Shell and sometimes other marine live forms. Some of these are color dyed to make them look attractive. However, this color treatment is rather obvious to detect. Below is an example of a very fine Natural Agatized Coral.
Agate with Mineral Inclusion
Mother Nature had “toyed” with the various kinds of minerals from its earth crust. Agates are found with Pyrite crysals, copper crystals, golden needles, fossils and in some rare cases silver or gold crystal inclusion. Some of these inclusion can also create a picture effect as well. The known treatment will be (same as picture agate) the foreign object insertion.
Hope you find this article useful. I will be updating this post regularly as soon as new treatments are discovered.
Note: Sellers with good business etiquette will always disclose all treatment that they are aware of on their gems. Always buy from sellers with good track record and reputation.