Monday, August 15, 2011

Gem Quality and Costs, Starring The Lovely Chrysocolla

How do you know what a gem cabochon is worth? There's no real grading scale, like there is for diamonds, but when I source cabs I look for several things.*

- Color is first and foremost. I like saturated stones and so do most of my customers. I look for consistent coloring. If the coloring is not consistent - many stones are multicolored - then consistent saturation or vibrancy of color.

- Cut, or technically, shape, is the second determinant. I like unusual stone cuts, but even if the shape is not symmetrical, the stone needs to look "balanced" to my eye. Otherwise it will likely look unbalanced when I try to set it.

- Quality. This sounds vague, but it really isn't. I define overall quality by the polish (or lack of), the regularity of the finished stone (for example, are the edges a consistent height? Is the back flat? Is the stone cut to show the best advantage of its qualities (transparency, luminescence, color)?

*Okay, it does kind of sound like a diamond grading scale. But there are no hard factors to compare the stones, just what I prefer.  :)

I'm going to use some chrysocolla examples to illustrate the points above. Chrysocolla is often confused with turquoise but its coloring tends to be more diverse and vivid, and it's often more "teal" than turquoise. In fact, much of it comes from Arizona, from copper mines. It gets its bright coloring from copper, as does turquoise.


Looking at the stone, I can see that there are uneven color patches. The upper left corner, for example, has a clear patch that will show when the stone is set. (Note: the two white patches on the top of the stone are from the lighting, but the area under the left side white patch is actually part of the stone). It also has a black stripe down one side. This will likely not be noticeable when the stone is set, but that in addition to the clear patch tells me that this is a stone I would not expect to pay big money for. Also, while it has good color, it has a more mottled effect than I would normally prefer (this will become more obvious when you see the next photos). There also some dark / black patches within the stone. Again - that is very subjective, but I prefer (and will pay more) for a stone without these dark bits. This stone is a nice quality, but not superb. Also, it's an asymmetrical stone - it's oval-y, but not really a true oval. That is not a detraction either, but the more cuts on a stone (i.e. sides of a triangle, rectangle) typically cost more money than a stone with less cuts, like an oval or round. And the non-symmetrical shape will definitely figure into design deliberations.

Side note: chrysocolla by itself is often too fragile to set in jewelry, but it is cut into cabochons when it is found mixed with quartz (the clear patches you see in some of these examples are the quartz).


More cuts:  higher price. More unusual shape:  higher price. What I consider better coloring:  higher price. And can you see the slight line running through the left side of the stone, to the bottom? I don't mind that in certain stones; however, I will pay more for stones without any kind of "fault" lines in them. The other thing you can't see from the angle of the first photo is that the semi-oval stone is of uneven height...more work when I set it. This stone has very consistently even sides. More labor / skill to make that happen:  higher price.


Another triangle. Notice that the edges of this stone are all a bit cleaner than in the triangle above it. The stone in the second photo has what I would consider "softer" corners. Usually, but not always, this speaks a bit to the skill of the cutter. And of course, more skilled labor costs more. Also there is no "fault line" running through this stone. It does have a bit of a clear patch on the left side but that will likely not show when the stone is set. If it does, it will not detract from the stone (I suspect it will be barely or un-noticeable). The two in the upper left are more noticeable on camera than in person. And the coloring and "definition" of the stone - by definition I mean the detail - is much sharper here.

And finally, the piece de resistance (of course I saved the best for last)!

Asymmetrical, again. But, to my eye, more "balanced" than the stone in the first photo.This has even more sides, so a higher price for that. Its coloring is not as consistent as in the second or third photo, but it has a wider color range. That is a very subjective point; I bought both stones, so obviously whether I want more consistency or more color overall varies.  :)  But notice the the colors on this stone are much deeper and richer than on any of the others (at least, I hope that comes through on your monitor). That will also typically bump up the price.

What's also interesting about this stone, though you probably can't see much of it in the photo, is that the edges are sort of beveled. The sides don't rise straight up toward the top of the stone; they slant inward a bit. See the two white streaks on the top sides of the stone? That's caused by the lighting hitting on those beveled edges. That's also a money factor. How it will work out as a setting factor remains to be seen. I have never set a stone (yet!) with edges like this. I'm guessing they will be a bit of a challenge. And you know how I feel about those!  :)

It's also really hard to tell from photos, because any polish I try to *not* have show so that you can see the full coloring of the stone. But the last two stones have a much more finished look than the second. The first one is also more highly polished, but because of the less vivid coloring it doesn't show that as well. In most cases, I am going to look for and purchase the stones with a better polish...probably because that usually coincides with a more sophisticated cut or shape, and typically a better color saturation.

So what are they worth? The first stone was less than half the price of any of the others. No surprise there. It's smaller in addition to the other aspects I mentioned. The second stone was a little more than double the first, and the last two were more than that. Chrysocolla is very prized for its vivid coloring, and tends to bring a commensurate price. Some of these cabs cost more than other lovelies twice their size. Partly this is because of the cutting and polishing, but partly it's just because it's chrysocolla. Such are the ways of the gem world...

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