How do I cut a stone with different colors on different axis’s?
This is a difficult question to answer definitively, but the rule of thunb is cut for the best color when you can. Naturally most of the time the best color is the narrow direction of the rough. So what do you do?
Well the first thing, of course is to try not to buy this type of rough. Unless it’s cheap and you want to play around. This is the easiest solution, but like everyone else you will still manage to acquire some of this rough.
You will see a lot of this type of rough for sale by the way. Guess why? Right, this rough is usually less desirable and often sold by dealers (who are usually perfectly aware of this) to people that are unaware of the problems. Buyers beware… There is nothing wrong with this (all is fair in love and faceting…), you just need to be smart enough to know what is happening and either not buy this type of rough or buy it cheap knowing that you will need to work around the problems.
In other words, the top material is very often cut in the dealers gemstone case, and what they judged to be lower quality in a cut stone is sold rough. This is not always the case, but it often is, especially in the cheaper rough categories. Remember it is human nature, the dealer wants to make the most money they can and the better stones bring more money and are naturally easier to sell when cut. After all they are in business to make money. You should not hold it against them, it is just business.
The second thing to be aware of is… Are the colors of the two axis’s complementary? If you do not know or are not sure what I mean by this here is an article about them.
If the colors are not complimentary, you do not usually want the rough. Here are a couple of other articles that you should read.
At left is “Samurai” in green Tourmaline – 7.3mm x 8.4mm x 5 deep cut by Jeff R. Graham Notice the color of the Tourmaline (left), it is a very nice Kelly green with some blue/green and yellow/green color. This is a very bright stone and actually came out better than a lot of people might expect, if they were just looking at the olive color on the “c” axis. This stone, because of the shape of the rough, had to be cut on the “c” axis which was the less desirable color axis. But because the a/b axis was a very nice blue/green, I knew this would actually cut a nice green stone when the colors mixed.
Notice the color of the Tourmaline (left) on the “c” axis, it is a darker yellow/green with some olive color in it. Not a color that I would generally consider buying and cutting. Because olive and especially yellow/olive/green stones are generally lower end color and just hard to sell. These colors are often not particularly bright in a finished stone either. But… on the other axis there was good color.
Notice the color of the Tourmaline (left), it is a very pretty blue/green. Too bad this rough was not wide enough to cut on this axis. This of course, is the best color and the color I would normally cut for. Even if I have to sacrifice some finished weight, blue/green is worth a lot more.
On this piece of rough I did not have a choice, the yield was on the “c” yellow/olive axis. Also notice that the a/b axis has a pretty large flaw (it was actually 3 flaws when I cut into them).
Note: I end up cutting a lot of this type of flawed material myself. I cannot sell it rough.
As you can see in the picture of the finished stone the colors mixed nicely and created a high end gemstone. In general the color that you cut for (looking through the table) will be the dominant color of the finished gemstone. But when you are dealing with complimentary colors, the color on the girdle axis (whatever it might be depending on the stone) will often influence the color of the finished stone substantially. I would say that it will usually end up 70/30 to 60/40 (70 and 60 being the color through the table), in a standard brilliant design.
Remember that there are other factors that will influence the out come, sometimes substantially. The main one is the design that you choose to cut the stone in. Choosing designs for rough, especially problem rough, is almost an art form… and I will cover that subject in another article.