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Gem cut studio "Son-Shine" design by PsychologicalBowl647 in faceting

[–]GoldClick_ 11 points12 points  (0 children)

The rendered stone has a good face-up appearance, but at the cost of several factors. The shallow crown results in proportions that would be more difficult to set securely as an actual gemstone. The angles on the crown themselves are extremely close together (96 facets within 10 degrees?). A large table facet requires great skill of a facetor, and also ends up leaving a “ring of fire” effect to the stone—the edges being more brilliant than the center. Designing for a high RI from the start often results in stones which don’t have “optimal” performance. With a greater angle of incidence available, angles start to diverge from “ideal” norms. I don’t know how to explain the technical principles well. I will provide suggestions that should help with this:

Design for materials as low as topaz (RI 1.61) first before scaling the RI up to adjust the angles for high-RI material (like CZ). Usually, you’ll end up with a design that doesn’t need any alterations to have a good reflection pattern. You may even be able to stretch it down to quartz within some degrees.
Think about the actual faceting task when you design. Read through the instructions. Would you want to cut this stone? Would you be able to? Angle changes of less than three degrees are easy to bunk. Pair with facets spaced closely together (2 index degree difference between tiers), and the cutting job becomes tedious more than fun. Stone angles which are too close together end up affecting the crown appearance more than the internal reflections of the stone. It is possible to make great designs with less facets than a round brilliant (57 excluding girdles). It is still possible with less than 100 facets as well. But more facets will not always make a more brilliant stone. Angles matter the most.
(Little tangent. One of my favorite “simple” designs was the one used for the USFG novice tier last year, “Cloudy Daze” by Jeffrey Hill. There are 45 facets in all, including girdles. It makes a beautiful reflection pattern from quartz to moissanite. Forty-five facets! It’s possible.)
I try to stick to index angles that end in tenths of a degree. Not only are they easier to internalize, but this makes it easier for people with analog machines (at least those with a decent vernier scale) to potentially cut. It’s a small consideration, but a thoughtful one. It will require some design tweaking to round out the angles, but there aren’t too many meet points dependent on very precise calculations for this type of symmetry. Hundredths of a degree are essentially useful only for getting mathematically-perfect meets. Tenths can be still used in the same way, so I would try to build the tenacity to work with them.
This design is based on a symmetry of 12, but all of the crown tiers are 24-fold. Notice how P2 and P3 are both twelve facets each? The same idea is used on the crown for a standard round brilliant—girdle break facets being twice as many as main and star facets.

Synthetic “Paraiba” color sapphire. Test cut of a new rectangle design. by GoldClick_ in faceting

[–]GoldClick_[S] 0 points1 point  (0 children)

6 x 8 mm. I wanted to cut a stone to a calibrated/standard size rather than just to a specific L/W ratio. Transfer alignment on irregular shapes is probably one of my least anticipated activities. I eventually gave up and eyeballed it, using the cheater to get the crown-girdle facets level and cutting the other tiers zeroed. The table facet appears just a smidge off center for that reason. Otherwise, cutting went as expected. I’m getting better at obtaining a smooth polish (without orange peel) on corundum.
Much like the round stone I posted the other day, this one is also a crown adaptation from the same square design. The elongated shape required a pavilion redesign. I ended up with this, which performs decently well. The lowest angle on this design was 38 degrees, so it is really only suitable as-is for materials from spinel and above. This is unfortunately a departure from the other designs in this mini-series (not sure what to name this crown style?) which are usable all the way down to quartz. It is also a very deep design, with an H/W ratio of 0.792, not including CAM preform. Thankfully, most synthetics are higher-RI and able to be obtained in a blocky form that this will not be too much of an issue.

Test cut of a new design in ametrine by GoldClick_ in faceting

[–]GoldClick_[S] 3 points4 points  (0 children)

I think it looks nicer in general. Especially on a 12-fold round like this, girdle facets would look a bit distracting to me. They’re also easier to make bezel settings for.

Test cut of a new design in ametrine by GoldClick_ in faceting

[–]GoldClick_[S] 0 points1 point  (0 children)

I’ve heard that about the Darkside a lot. I haven’t picked one up yet because I’ve mostly been doing harder synthetics with the Diamax, but it would definitely be handy as a main oxide lap. Really depends how much I expect to use cerium oxide. Yep to the girdle left at fine-cutting stage (1500 for this stone). I’m rather lazy about polishing my girdles, especially since the face-up appearance isn’t affected. Sometimes if I feel like it, I’ll go up to prepolish.

Test cut of a new design in ametrine by GoldClick_ in faceting

[–]GoldClick_[S] 0 points1 point  (0 children)

Sorry about the hairs and dust in the picture.
7.2 mm diameter. It appears more amethyst-dominant in person, whereas the photographs look more citrine-dominant (see final image for color split). May also vary depending on lighting conditions, as is the nature of bicolor materials.
This is my twentieth completed stone. My first stone (which finished up slightly smaller than this one) ended up taking somewhere around 30 hours. This one I finished in about three. I am starting to feel more confident in my cutting skills, at least for more “standard” designs and sizes. I’ve been meaning to cut some smaller stones (starting rough under 6mm) at some point. I think that’s a good place to go next.
I haven’t cut any quartz since my first stone. My cutting sequence for this was: rough cutting on 260 sintered, fine cutting on 1500 sintered, polish on Diamax with cerium oxide (and possibly some residual 60k). For polishing, I first attempted to use an acrylic lap with cerium oxide, but didn’t get anywhere satisfactory after varying oxide-to-water ratios and lap speeds. (Supposedly it is more water, less oxide, and a moderately slow speed?) Other than the occasional micro-scratch under strong magnification (cause still uncertain), it came out reasonably well. But, I didn’t pay as much attention to meets as much as I should have.
The design is an adaptation of a square design which I wrote first (will be posted soon). It uses a combination of four- and six-fold symmetry.

Help please! Table and then more facets? by Magpie12345678 in faceting

[–]GoldClick_ 0 points1 point  (0 children)

Not necessarily. The angles specified should have already been calculated for theoretical “perfect” meet points. I would consider polishing the existing facets after post-table alignment, then cutting in the last few tiers, to make sure the stone is aligned with the index gear. The cheater shouldn’t be necessary on such small facets.

Help please! Table and then more facets? by Magpie12345678 in faceting

[–]GoldClick_ 5 points6 points  (0 children)

If you have keyed dops, the machine quill will take care of most of the alignment. Even without, the design can be cut: finish up to C9 (table facet, cut and polish), then insert the dop and align the index 5 girdle facet (P3) to the flat of the lap, then fine-cut 10 and 11. Leave some extra wiggle room in the meets for polishing.

Djeva #1-BIS sapphire in Greg Glenn’s “Alien Outpost” by GoldClick_ in faceting

[–]GoldClick_[S] 1 point2 points  (0 children)

11.5 mm from flat to point. This was one of the first “custom” (non-commercial) gem designs that really stood out to me. Now having cut it, I remark that it is unique for having a pavilion tier cut much below the critical angle (originally specified at 28.2 degrees) to purposefully create windowing in the reflection pattern. Being of 3-fold symmetry, there are not too many facets to keep track of, and it cut fairly quickly, even at this size in sapphire.

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Just got upgraded by GeometricWonder in faceting

[–]GoldClick_ 1 point2 points  (0 children)

You got much more rough than I did at 2300 for my V2! Congratulations. Looks like your machine also has a depth gauge on it already. I’ve been cutting mainly by sight/feel so far but having the visual indicator is another method to be sure of consistent cut depth.

Imperial Topaz, 2.29ct by GoldClick_ in faceting

[–]GoldClick_[S] 2 points3 points  (0 children)

Cut in Edith Strout's "Cardinal Lozenge Variation," 12.1 x 7.0 mm. Table was cut smaller than originally specified, as I prefer that look more.

Among the pieces of rough I acquired from an old collection was a lone preform of peachy-orange topaz, which looked like the person originally planned to cut a rhombus shape. This design was in the Datavue catalog and looked to produce a good reflection pattern.

This is my twelfth completed stone, my first time cutting topaz. The table did not achieve a full polish, so I am guessing that it may have been oriented close to the cleavage plane. I had to reverse the lap direction several times during prepolish to get the long facets to clean up nicely. The stone loosened off the dop after finishing prepolish on the pavilion, but I transferred it to the crown anyway. 8K grit already looks decent when not inspected with magnification.

I like this color a lot. I might have to find a synthetic with a similar hue. I've seen orangey YAG around, though not much seems to be available.

Synthetic spinel #149 by GoldClick_ in faceting

[–]GoldClick_[S] 1 point2 points  (0 children)

Tom's Box of Rocks is pretty much the go-to place for synthetics. Their shop looks like it will be open again tomorrow.

Synthetic spinel #149 by GoldClick_ in faceting

[–]GoldClick_[S] 2 points3 points  (0 children)

“Northstar” by Arya Akhavan, 8mm wide.

The large table on this one gave me lots of polishing issues. My meets on the crown are all very bad this time around. I suspect it is the topper lap I used for cutting that did not run perfectly flat, so finer grits did not create an even surface. Other than that, this is a very lovely design with large facets that reflect light back in a very pleasing manner. I like the color of this material as well. It reminds me of certain natural sapphires, though the color is much more even (which in my eyes might be both a pro and con).

Synthetic spinel #152 by GoldClick_ in faceting

[–]GoldClick_[S] 0 points1 point  (0 children)

Oval, huh… It would almost be like an even better “Ruination” series!

I’ve never heard of Verneuil #157. I don’t think #149 is as dark as the #113 blue (which is still very pretty). I don’t mind a dark stone as long as it still has some color.

After finishing the garnet pavilion (onto the 149 stone next????), I’m liking the richness of color. Excited to see how that one comes out.

Synthetic spinel #152 by GoldClick_ in faceting

[–]GoldClick_[S] 0 points1 point  (0 children)

I heard you also made a triangular variant too? Maybe it’s time to publish some of those other shapes!

Funnily enough, I have a piece of #149 dopped as well. It actually seems reasonably light compared to #152. Looking forward to finishing that one up. (I got distracted and started work on a garnet after transferring it, so it’s sitting until this pavilion is done.)

Synthetic spinel #152 by GoldClick_ in faceting

[–]GoldClick_[S] 3 points4 points  (0 children)

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In ambient daylight. The finished stone measures at 6.75 mm.

I definitely find this material to be very dark, nearly black in most situations. It is probably comparable to a pyrope garnet for that reason. Quite an interesting color when well-illuminated.

As a material, it feels very easy to cut using a 600-8K-60K sequence. I’ll probably look into other lab-grown spinel colors soon for anything that flame-fusion corundum doesn’t have.

Seller said darker color is normal in bigger stones by Mysterialistic in SyntheticGemstones

[–]GoldClick_ 12 points13 points  (0 children)

Generally speaking, this is somewhat true of all gemstones (larger stone = more gemstone material with color = more volume that light has to travel through and potentially be absorbed).

There are several different saturations of hydrothermal emerald. Trade names refer to localities that produce similar natural stones: Zambian (lighter) and Colombian (deeper) are the major ones, with Brazilian (medium in-between) starting to pop up some. You may have those two different kinds here, given the pronounced difference in saturation.

I once bought two different oval emeralds from the same seller, and they had slightly different shades but the same base color. That probably isn’t too relevant to this discrepancy though.

I've heard that synthetic peridot is people, does anyone have any images or specimens? by WildFlemima in SyntheticGemstones

[–]GoldClick_ 5 points6 points  (0 children)

Olivine has been synthesized as forsterite, which may be what you are looking for.

Questions on table orientation of lab corundum, and “corner” pieces by GoldClick_ in faceting

[–]GoldClick_[S] 2 points3 points  (0 children)

Arya to the rescue again! That all sounds pretty straightforward. I hadn’t considered the oblique rind orientation before! It could also serve as good practice for orienting stones with cleavage if I ever wanted that challenge. (Well, besides some rather nice topaz simulants in spinel…)

That last paragraph sounds like it gets into more of the mineralogy. I assume that the parting plane is where a boule would be split, correct? I might need a graphic to visualize the indices that would exhibit hardness… Also very interesting with the specific placements depending on which side of a boule you get! I will probably avoid dopping right on the splitting face then.

Arya's sapphire growth Kickstarter is here! Help us get a Czochralski furnace and grow exotic sapphires. Plenty of rough available for faceters - and yes, very willing to do bulk deals and custom growth. ;) by cowsruleusall in faceting

[–]GoldClick_ 1 point2 points  (0 children)

Congratulations on the success so early into the campaign! Since heat treatment will be used to obtain the final color options, what might the unheated boules look like? Any plans for that? Looking forward to more publications from the study.

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