“Man is the measure of all things”
“Cabochon Cut; method of cutting
gemstones with a convex, rounded
surface that is polished, but unfaceted.”
The art of cabochon making is one of reading. If I were to ask you to recall a very good book from your youth, which one would it be? What parts would you say were exciting, or memorable? To me, when a guest walks into our lapidary, and they ask me what stones will cut the best, I feel that I’m looking through different stories and picking out not only the most interesting ones, but also the best parts of them to showcase in order to make stones that they will remember for the rest of their lives.
Every rock has a history to it, which can be discerned by it’s current state. Often times, this can be made the central aspect of a cabochon. However, in order to read a stone, you must have some geologic understanding; in the same way that you must understand a written language in order to read. Through the course of my postings, I will attempt to convey the terminology, concepts, and methods by which rock might be evaluated, and lapidated into the cabochon form.
The science of cutting en cabochon is best described qualitatively. There are fewer numbers to consider than with other cutting methods, such as faceting. The aspect of rock which I read is called fabric, and the aspect of crystals which I read are their orientation.
Fabric describes the spacing of elements that make up a rock, and for our purposes, is considered in the same manner that a painter would consider the visual flow, and color of a work. When I say “elements”, I’m talking about an intermingling of minerals, and structures (such as bedding, banding, metamorphic textures, phantoms, fossils, etc.).
Orientation of crystals has to do with their base chemical structures, and how these structures interfere with the passage of light to produce unique optical properties. This can be anything from pleochroism (color changing stones), to asterism (star stones, which appear as dots of light that ideally have discernible rays), iridescence (an illuminating color change due to structural interference of light), chatoyancy (shimmering beams of light, or “cat’s eye” stones, otern due to fibrous inclusions and structures), etc.
To show an optical property, I tend to affect the rough (raw material) by grinding or cutting at a desirable angle to adjust the viewable surface (prior to shaping), such that the visual property will be seen on the table (domed top) of the finished cabochon. That is to say, if I were to lay a cabochon directly under a light, you would see the stone illuminate with its intrinsic optical effect.
When worn, the visible result is a roving light, which will dance across the surface of your gemstone, and for every light source there is, the effect will intensify. There are similar optical properties found in the fabrics of rock, and it is even possible to reduce the appearance of fractures (or even display them) in clearer stones through proper orientation.
However, out of this edition of Cabbin’ Fever, I hope that I have conveyed, if briefly, some of the desirable qualities that I look for in the rough hewn rocks and minerals when I consider them for a polishing. I strive to make something that people find to be personally beautiful, and would like to share my knowledge on the subject where I can.
Out of later editions I hope to expand on some of the aforementioned subjects, and explore new ones. If you’ve liked this as a teaser, feel free to write in questions, and topic suggestions.
C. Willis Riffe