What Are The Different Types of Opals?
There are basically six distinct types of natural opal including black opal, crystal opal, white opal, fire opal, matrix opals, and boulder opal. The first four in this list are all solid opal while matrix opal and boulder opal have the host rock included. Boulder opals consist of a layer of opal that has formed in crevices of the host rock ironstone. When the stone is cut the host rock is left on the backside of the cabochon. This provides a dark background to the thin layer of solid opal. This is also left on for strength, as the thin layer of opal would be too weak on its own. Matrix opal is ironstone or clay stone in which the opal material has formed into the pores of the host rock. This type of opal is treated with a sugar solution and then acid to carbonize the sugar and create a dark background. Without this treatment the host rock appears brown and masks most of the play of color.
Black opal is solid opal that has a dark or black background tone, white opal has a light or white background tone, and crystal opal has a transparent background tone. Fire opal has an orange or red body tone and comes primarily from Mexico. Australia produces most of the high quality opal although various types can be found worldwide. Black opal is the most highly sought after type of opal followed by boulder opal, crystal opal, and fire opal. Matrix opal and White opal are the cheapest types of opal but still can reach hundreds of dollars per carat in their finest forms. Pictures of opals can be seen at www.directorygemstones.org.
nice article and I just bought a matrix opal from you.
Excellent. thanks
thanks again for the article.. been on your post about gemstones photography, now im seeing this and looking at the opal gallery..
Hi,
Thanks for the article, I just wanted to clarify some information about the treatment of opal. There are a few different types of Opal that do require treatment. The Opal from Andamooka which does require treatment in a sugar solution (and then acid) is I think the one you are referring to above. There is also another type of Opal called ‘fairy Opal’ or ‘sandstone matrix’ which comes from Queensland and the Opal is scattered through sandstone. Untreated, it just looks like brown sandstone when cooked in ‘palm oil’ for a period over 12 hours, the stone turns black and then all the colour is shown. What is now commonly know as Boulder Opal Matrix is not treated but completely natural. It is a brown ironstone and has what looks like many fiery spider webs all mixed upto together.
I am also building up a page of useful and interesting information about “boulder opal”. Here is the link…
http://www.quality-semi-precious-jewelry.com/Boulder-Opal.html
All the best
Geoff
http://www.jgjewellers.com.au
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gemstones are expensive but when you give a ring with gemstone to your girlfriend, she would really like it -,;
This is a great article. I am an opal dealer and did not know half of what you were saying and now i do! I have matrix opal, from australia. Some people call it boulder opal… Also what is the lightening ridge opal! I have a type of fire opal from ethiopia it called chocolate opal and it has amazing fire! The newest fire opal i have is from Sudan and its great for cutting, this is much better then the ethiopian opal as it didnt cut very easy. It will cut but is easy to break. Thanks again for the great article and let me know about the lightening ridge! I have some other dull green stone the man sold me he said was opal. I have not tested it so i am not sure!
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I just read the comment by Geoff and the link to more info on the boulder opals is great. This answered the question i had just asked above.
So thank again. I have many thai friends who are professional gemstone cutters. let me know if you need any work!
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Thanks again,
Iain