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This is just in from the mail bag:
I can't thank you enough for recommending the 600 cutting lap and BA5T to pre-polish with 3,000 diamond powder and then to use the BA5T for the final polish with 50,000 mesh diamond powder for cutting corundum. I purchased the 2 BA5T's and the 600 cutting lap. I just finished cutting my first Montana sapphire using this system. What a joy to use the BA5T's. I polished the sapphire like it was butter. It cut my pre-polish and polishing time by at least a factor 4. It polish those nasty tiny pits right out of the stone in nothing flat. The only thing I have to watch out for is overheating when polishing and cutting back on the pressure applied especially with the small sapphires. Again, a big thank you! Your recommendation is a huge time saver and it makes cutting and polishing sapphires a joy rather than dreading the polishing time.
This guy is following my recommended sequencing for cutting and polishing Corundum. It’s great to see someone getting the FUN results that faceting should be providing. How many more stones will a person cut when they’re having FUN doing it? This kind of feedback is the reason I built this site. Thanks very much!
This just in from the e-mail bag:
I started to facet this piece of Sunstone yesterday and when I used the 600 lap this strange surface appeared on this particular facet and it wouldn’t polish away, any idea what or why? What amazed me was that it only happened on this one facet, the stone is approx, 10 x 14 mm.
You usually see this sort of thing on Sunstone at the pre-polish level if you’re really close to a cleavage plane. Often, a sensitive faceter will detect this potential while cutting because these facets will feel softer than the rest – will cut faster, and over-cut quickly. The solution to getting a polish on them is:
Usually, a combination of these things will let you get a good polish – though we must sometimes settle for an over-cut facet in the process.
I just received another e-mail from someone asking about re-cutting a native-cut stone. Someone apparently offered to re-cut the stone, and:
"it would likely only need the pavilion facets straightened out, and the the bulges removed from underneath ... so the stone wouldn't even lose a carat".
Most of the windowing fat-bellied stones we see, the pavilion is roughly a hemisphere. That’s the bulges [sic] someone is referring to removing without losing a carat. Modern brilliant-style pavilions with “straightened out” facets are roughly cones.
So, to evaluate the “straighten out and remove bulge without losing a carat” statement, let’s look at some 7th grade math:
The formula for volume of a hemisphere is: 2/3 * pi * r^3
The formula for volume of a cone is: 1/3 * pi * r^2 * h
The volume of the cone will be ONE HALF the volume of the hemisphere, provided there’s sufficient depth to support proper angles without reducing the gem’s width – a luxury we usually don’t have. So, the yield is often less than 50% – a fact many customers find shocking.
Given that many native-cut stones are grossly lopsided, as well as too shallow to support their existing width with proper angles, a great deal more than 50% would be lost re-cutting many of them. Here’s a roughly profile-angle photo of the Sapphire re-cutting job you’ll find further down in the blog:
This stone was originally 3.5 mm deep, and we re-cut it to 3.2 mm deep, centering on the deepest portion, and losing only 0.3 mm in the process. The finished gem looks like this in profile:
To see the before and after of face-up appearance, have a look at this post.
Many faceters don’t keep a book on their actual yields, and wind up quoting insanely hopeful stories to potential customers. I recommend keeping a careful record of what you cut, and how you yield. Staying in touch with reality – and helping to improve performance are both very useful in my opinion.
This question came via eMail today:
As diamond laps are very expensive and their diamond surface is a thin layering, have you heard of major producers of these laps offering any kind of reduced price to resurfacing worn laps. I use the Crystallite steels and it just seems like they would be one that would be a re-surfacable item. Your thoughts?
I am not aware of a re-surfacing operation by any of the major manufacturers. I’m not an expert on the diamond plating process, so I don’t know if there’s a reason this could be more costly than starting fresh. I assume there are contamination issues, and that producing a quality product would require stripping the old diamond away – and that may be problematic. That’s a guess.
In my experience, there’s seldom a need for high-quality precision laps in grits more coarse than 600. And, good working with the 260 and lower (more coarse) grits will minimize the wear and tear on the 600 metal bond. And, treating the lap nicely (water, not too much pressure, etc) will also invite it to last a long time.
My Crystallite 600 laps last me years of pretty heavy use.
Hope this is useful.
This is a natural Sapphire recut of a native gem that was pretty bad in terms of geometry and color presentation. There was a chip at the girdle, lopsided geometry (check where that culet is), bad meets, bad polish, and abraded facet junctions from the typical mishandling often found with native stones:
Original was 8 x 6.3 x 3.5 at 1.7 carats weight. As is typical with very shallow stones, the re-cutting lost a great deal of weight. Finished dimensions are 5.25 mm diameter, 3.2 deep, and 0.52 carats.
However, the presentation is a great deal more eye-catching — even from several yards away:
The color is actually a great deal better than I could capture here – with a very saturated electric orangy-pink. The re-cutting also removed two included crystals and most of a veil that was originally toward the thin end.
I selected a 9-main Round Brilliant with un-stacked Mains – to work with the depth restriction while creating max scintillation and saturation retention. Check out this video:
Quite a stunning custom engagement ring stone. Now, for the platinum…
This is an article about gemstone prices that’s important to STUDY – not just skim – about the story your pricing tells – and how you tell your story through your pricing. This is part of the core business skills material we cover in the live Academy, but perspective and continual exposure to these principles is important. Please read it:
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Someone recently asked me: “Do you use a polariscope to determine (locate) the C axis before you dop the stone?”
The short answer is “No, that’s not necessary”.
The longer answer is about why you don’t usually need a polariscope to locate C axis in materials where C orientation matters. There are three reasons to orient according to optic axis when dopping:
So, by the numbers (1), two of the most common structural concerns are the examples I used above – Topaz and Spodumene. Both of those materials usually have enough directional color that in a water-worn pebble (or even a polished sphere), a faceter who knows the material can orient the C axis readily just by knowing that color intensity is greatest on the C axis – and temp-tabling carefully.
When C axis orientation is a consideration for reasons of color (2), such as in the examples of Corundum, Spodumene, and Topaz – this is because the color is in fact different (better, more desirable, more intense) in that direction. So, anyone who can notice color can readily orient the rough to the best color direction. All that remains is to dop carefully in that direction.
Lastly (3), when facet doubling is a concern due to birefringence, one may use a polariscope to locate the optic axis. However, this is going to be a very rare case because facet doubling isn’t a standard consideration for an appraiser. It’s not going to reduce the value of the finished stone, while a reduced yield will. And, orienting strictly for optic axis in a gem where that doesn’t affect color may well degrade yield. In other words, unless there’s some unique and compelling reason that applies to a specific stone, there’s no justification for it.
A polariscope is a useful tool for many things, but a faceter with the standard knowledge we expect of Faceting Academy graduates won’t be reaching for one as part of the dopping process because they don’t need anything more than their eyes and their knowledge.
To learn more about opportunities for building this important and standard knowledge yourself, explore the Faceting Academy web site further.
As you begin to build your web site, you’ll be wondering how to get traffic onto the site. An important way to achieve that is to have high-quality, relevant inbound links directing interested people to your site.
It would be great if those links were in ideal locations; if you didn’t have to pay for them; and if they were more or less permanent – so every one you created would remain in place once you took the time to make it.
And, one way to do that is …
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So, although a bit Springer-esque, I think you get the point of this post – the same point I’ve made repeatedly with apprentice faceters: The “competition” isn’t really even in the game with you – not even on the field. And, if you take a little initiative and invest a little, using what I’m showing, you can smoke them – and position yourself quite strongly.
So, even if you’re not at this point in your site development YET, it’s not too early to do some preliminary research and draw some plans.
One of the Apprentice Members asked if I would share my Gemstone Certification card (the one for ID and Provenance) to maximize value. And, of course, the template for that card is included in this post, below, because I’d like to see all the really professional faceters I know using a gemstone certification card of similar type – to build that into an expected standard of doing business with American lapidary artists. This can only improve the depth and quality of the market for all, while expanding subjective value for our clients.
If you attended the resident Academy, you may remember me telling the story that this document originated at the suggestion of my friend, professional appraiser Reggie Olson, who was coaching me in the principles of “Perception of Value” – and in the concepts behind a jewelry appraisal. Reggie not only inspired me to create the program, but had a strong hand in its design.
The purpose of the gemstone certification card is twofold:
A. Document the provenance of the gem, under the hand and signature of the cutter. And…
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Someone noticed that on GemstoneArtist.com I am calculating gemstone prices down to the penny. And, they asked me about my methods for calculating gemstone prices.
First, I use The Guide – which is the de-facto standard reference (at least in USA) for appraising gemstones. As with my cost-based formula, I recommend using some Guide information before you buy the rough – and before you cut. For instance, if there’s a premium for cushion shapes, why would you cut a round?
Second, I use a formula based on my cost and my time invested. And, I recommend applying that formula before you even buy the rough – to determine if it’s reasonable to get paid for doing the faceting. (Details are disclosed below.) This formula is also modified in a specific way, based on …
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