Facet Math.

[@CurrentlyRockhounding]

"Say you have a perfectly spherical alluvial sapphire with a diameter of 10mm" 🤣

[@delilahamiano7751]

Thank you, Patrick. I'll be watching this one over and over again to have the math sink into this brain. Oh, I mean girdle. LOL

[@kenwin5845]

I've never seen someone facet a meth crystal

[@MiningAmerica]

It seems that you found your proper voice and editing style for KZbin. Keep with this, it should go strong.

[@pigeonbloodruby5330]

I was thinking the same, good voice for narration.

[@kaydavis8872]

Thanks for this explanation.

[@pjk1714]

Nice you provided this one.

[@Algoldprospecting]

Great information. Just getting into Faceting. I got a lot to learn

[@Ken_G.]

Numbers. Next to coffee, the most important part of my wake up routine to get the brain firing. Thanks Patrick. Great vid. Too bad that perfectly round sapphire has so many fractures.😆 Better as a specimen anyway. It's neat to see how the law of diminishing returns translates into faceting. Controlled aesthetic entropy at its finest.

[@sarahinscotland]

Because math 🥲

[@largent45]

I know its a calcuable math, but its nice ro dream, if just for a moment , of that perfect la ge stone. We can get practical later! Before xutunt for sure, bur later!

[@pigeonbloodruby5330]

Good topic. I'm using 30% yield when purchasing rough opal. I like the quick rule of thumb for gems 1g=1ct. I'm looking for a rough lump of VVS black spinel, also called Thai black spinel or Black Jack spinel. Any tips of how to judge rough black spinel to be of gem quality? I'm not gem cutting (faceting), I'm cutting a geometric pattern. FYI, There are two general heat treatment methods for gems. One is low temperature and the other is high temperature. Higher temperature heat treatment of sapphire is 1800C and can be held at temp for 10 days. I suspect that the temperature ramp up rate and hold times during the ramp up and ramp down heat treatment is important. Tks!

[@DonohueLabs]

With opaque stuff I don't know how to judge other than doing a test polish on an area. With spinel the only thing I've heard is that alluvial is more sought after as it turns out better. Overall I'm still very new at gem rough buying and grading and tend to stick to reliable sources so I can trust they are selling a good product. But I know that doesn't work in some cases if you're looking for something very specific.

[@AJShiningThreads]

The pavilion cut is a relatively modern creation, isn't it? Back in the day before the pavilion cut was invented would the goal have been to keep more of the stone intact?

[@pigeonbloodruby5330]

A few weeks ago I read a paper on the history of gem faceting. In ancient times and for 1000's of years a well terminated gem was the ideal. Then came faceting and the first cut was called a point cut. Still trying to retain the original natural terminated points. I just purchased a doubly terminated spinel specimen. I'm having a difficult time designing a setting for it.

[@MrJackhammer51]

The usual would be a cabochon cut, which normally should retain more weight. Although the emerald cut comes very close to the natural shape and would probably cut a bigger stone. So there are exceptions.

[@DonnaChassie]

Patrick? I have a new three hundred dollar faceting machine called a Vevor. Looks accurate, But! I haven't faceted anything yet. I'm planning it all out and my problem is transfering. There is no index pin or flat spot, in the quill. I can fix that with a small drill and then a center punch. The problem is how do I find the center of the dop...both dops, when both are in the transfer jig? I have about ten dops of brass. I guess I could notch each one. I know If my Lead Man were here, He'd know. I'm in Graham, on the other side. Hope to meet you, this Summer. Donna Chassie

[@DonohueLabs]

Index pins only make it easier. You can transfer to the other dop and then line it up on your faceting machine after the fact if you have a faceted girdle. Set your machine to 90 and lower the stone onto the master lap and adjust it until the girdle rests flat across the lap. It's easier if you have a machined block that's perfectly square to raise the stone up a bit. But as long as you get it close to square, you can make fine adjustments with the cheater after making a few cuts. Leave yourself enough meat on the stone to make those adjustments because you may need to make a few passes around it. Another option is to cut a round (or mostly round, like with 16 girdle facets) stone and don't worry about the alignment. A standard round brilliant will look good even if the crown and pavilion aren't perfectly aligned. Your girdle will look a little wavy, but that's actually how most commercially cut gems look.

[@DonnaChassie]

Thank You, Mr. Donohue. I will do as You say. I will build my skill, transferring, without needing index pins. I can see myself, taking a very light cut, to see how I might adjust the cheater knob. I expect I will pic a dark rough six X eight mm garnet, and, first, make the girdle, using four sides, to check how accurate the frame is. Then I'll do the pavillion with four facets, looking for a pointed pavilion. Then, change dops, the new way You have taught me, and make a crown, some how. Then, I'll pic a stone of some kind, use the standard round brilliant plan, since the cut will look good, anyway. But, I wish for accuracy. I'm so excited. Donna Chassie@@DonohueLabs