“Successful design is not the achievement of perfection, but the minimization, and accommodation of imperfection. “
A guest entering our shop will notice many items of interest, a few see the machine they see me working on, and ask me about it. Mostly about obvious things, like, what it does, what sizes of grit it uses to shape, and polish. Some will also see that the water in the machine is of varying colors, and some see that there is water at all.
Primarily people will rightly guess that the water helps keep the dust down, out of the lungs, off of other wheels. Yet, there is also lubricant in the water, as the water basins serve the dual purpose of cooling wheel and stone.
In fact, there is even more, and less obvious, water present in the air, or even in the hewn rock that I work with, which has been exposed to water recently, even if it had sat in an envelope for a few months. This is because most rock has natural gaps in its matrix and/or ground mass (i.e. fabric).
Sometimes, these gaps are small vugs, gaps from dissolved, or otherwise eroded minerals. Natural porosity, due to the consolidation of grains in sediment, gaps between crystals (consider a grain to be round, and imagine filling a box with circles). Or, even worse, in a fracture.
After all, once a fracture develops, it will almost certainly propagate. Especially if the water within the rough overheats, expanding its separation. However, due to the use of lubricant enriched water. The most trouble I typically see are in the final stages of polishing, either from polishing powder that has not been regularly wetted, or even from processes involving extending fluid on diamond powder and paste. There is something frustrating about certain materials, like the garnet, apatite, fluorite, or even the beryls and topaz when exposed to an expanding drum. They fracture in the blink of an eye, if not kept cooled with regular water dipping.
On occasion, imperfections can be awesome inclusions in a finished cabochon, but these are usually seen prior to working the material. Fractures that were developed via variably heated regions of stone within the earth, or even forming from dropping on a lapidary floor.
Like with a fiery faceted stone, there may occur veils (microfractures) which break at just the correct angle, or even become filled with an impurity, which diffracts light into variable colours, depending on the material. In our shop, we simply call these rainbow fractures, and can occur in just about any type of transparent/translucent rough, while giving it the sort of awesome beauty typically found in precious opal.
The caveat with this quality is that, again, fractures propagate, and this sort of stone will split first along it’s most desirable quality, if given the opportunity. Many times, fractures are desirable in that it will give a stone a wispy quality to its texture, and may darken a cabochon, intensifying its colour.
Other imperfections, such as the gaps mentioned earlier, or even mixed materials consisting of variable hardnesses, will polish with an irregular finish that are comparable to one another. The often produced effect for a troublesome material is a mat finish, but, more ideally, we can achieve a mixed polish, bearing areas of high and low gloss, such as you might find in some types of dinosaur bone, or with ruby zoisite, where it’s green mica (fuchsite) takes a naturally waxy luster, while the ruby takes a high polish.
Crystal pockets in a rough stone are another quality which may be a pain or yield ideal appearances. It’s kind of awesome when you yield a stone that shows tons of little quartz (or other) crystals sparkling among the surrounding flow of colors.
That’s most of what I have to say on the incorporation of fracture en cabochon, if there is anything that you would like elaborated, or would like me to cover in a later edition, feel free to email me.