claudenancy
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Although sometimes thin layers of gem opal that are attached naturally to potch or matrix are called "natural doublets" they are universally distinguished from doublets that are created by attaching a backing to an opal. The term "doublet" generally references the latter artifically attached variety.
Opals that are naturally attached to a base (e.g., potch or ironstone) are not classified for evaluation as doublets.
For example, if the natural backing is ironstone the opal is classified as "boulder", and evaluated using criteria for boulder opals and if the backing is potch the evaluation is usually based on criteria for solid opals(see Paul Downing's Opal Book series).
Having studied opals for years, I have had some experience with older opal doublets that were made in the early days of the Australian opal fields. These are far different from the very thin commercially cut doublets of today. Many publications on opals suggest that there were no doublets made prior to the 40s. However, this is incorrect, and early opal doublets are documented in recent Australian sources.
Most of the literature on opals address only the typical commercially cut doublets that are inexpensive and readily available in the market. There is a real absence of information on evaluating the early doublets, or atypical doublets that might be created by different process todayl
It is now well documented that doublets were manufactured as early as 1897 in Queensland. Apparently in these early days of the opal fields there was wide variation in the materials, manufacturing process and quality of both the backing material and the opal material. In fact there are some older doublets that were made with very high quality opal material. Also there are documented examples of high quality opal in doublet form. I have an early doublet that is backed only by a thin slice of clear opal. The background color as well as fire of the opal come exclusively from the upper opal material itself. Apparently these early opal "doublets" were often created to preserve quality opals that had relatively extensive "faces" and would be very fragile if cut to preserve the surface layer as a single piece and not backed ( These were relatively thin but not razor thin like modern doublets that are mechanically sliced so that many doublets can be made from already thin material.)
For years I tried to document exactly what my doublets were.
Last summer I was able to sit in on an opal class that was being taught by Sara Boyce, a student of Paul Downing. THe class examined a number of my opals using an electron microscope, and also the settings for the opals. They confirmed exactly what I described above--early opal doublets with high quality opal on the face. The largest opal doublet (picture attached) was backed by a very thin, low grade clear opal--something neither Sara nor anyone else in the class had seen before. All the color, as well as the fire, originate in the surface opal. The mountings are rose gold and are in the style of, and appear to be from the period of the very early 20th century. I also was able to purchase a new Opal Book from Sarah, in which the existence of opal doublets made in the late 19th and early 20th century, primarily by small shops near the original Opal fields in Australia, is well documented. THe book is "Opal--The Phenomenal Gemstone" , edited by Clifford et. al. and published in 2007.
Opals that are naturally attached to a base (e.g., potch or ironstone) are not classified for evaluation as doublets.
For example, if the natural backing is ironstone the opal is classified as "boulder", and evaluated using criteria for boulder opals and if the backing is potch the evaluation is usually based on criteria for solid opals(see Paul Downing's Opal Book series).
Having studied opals for years, I have had some experience with older opal doublets that were made in the early days of the Australian opal fields. These are far different from the very thin commercially cut doublets of today. Many publications on opals suggest that there were no doublets made prior to the 40s. However, this is incorrect, and early opal doublets are documented in recent Australian sources.
Most of the literature on opals address only the typical commercially cut doublets that are inexpensive and readily available in the market. There is a real absence of information on evaluating the early doublets, or atypical doublets that might be created by different process todayl
It is now well documented that doublets were manufactured as early as 1897 in Queensland. Apparently in these early days of the opal fields there was wide variation in the materials, manufacturing process and quality of both the backing material and the opal material. In fact there are some older doublets that were made with very high quality opal material. Also there are documented examples of high quality opal in doublet form. I have an early doublet that is backed only by a thin slice of clear opal. The background color as well as fire of the opal come exclusively from the upper opal material itself. Apparently these early opal "doublets" were often created to preserve quality opals that had relatively extensive "faces" and would be very fragile if cut to preserve the surface layer as a single piece and not backed ( These were relatively thin but not razor thin like modern doublets that are mechanically sliced so that many doublets can be made from already thin material.)
For years I tried to document exactly what my doublets were.
Last summer I was able to sit in on an opal class that was being taught by Sara Boyce, a student of Paul Downing. THe class examined a number of my opals using an electron microscope, and also the settings for the opals. They confirmed exactly what I described above--early opal doublets with high quality opal on the face. The largest opal doublet (picture attached) was backed by a very thin, low grade clear opal--something neither Sara nor anyone else in the class had seen before. All the color, as well as the fire, originate in the surface opal. The mountings are rose gold and are in the style of, and appear to be from the period of the very early 20th century. I also was able to purchase a new Opal Book from Sarah, in which the existence of opal doublets made in the late 19th and early 20th century, primarily by small shops near the original Opal fields in Australia, is well documented. THe book is "Opal--The Phenomenal Gemstone" , edited by Clifford et. al. and published in 2007.
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