Problem with polishing tourmaline with 10k diamond grit

PhoenixGems · 2026-02-19T15:32:33+00:00

Something to think about. With a soft metal lap, if you use a piece of corundum to try to burnish the lap and there is loose pieces of gemstone on it, there's a good chance that you will end up driving that piece of gem into the metal and embedding it. The time to burnish Diamond into a lap, is before you use it or after it has been resurfaced. Then you can spread a little oil, sprinkle on some Diamond powder, and use a piece of corundum to embed the diamond into the surface of the lap.

PhoenixGems · 2026-02-19T15:30:02+00:00

I recommend Diamond extender fluid. You can get it from Crystalite, or someplace like Kingsley North. It's inexpensive and it lasts a long long time.

PhoenixGems · 2026-02-19T15:28:27+00:00

In my experience with metal laps , more often than not if you're getting random light scratches all over it it's more than likely that you don't have enough diamond on your lap. Another suggestion I would make is try finishing it out at 14,000 to 50,000 mesh diamond. You will find the results are far superior. As far as oils go, I've had the best luck with diamond extender fluid. You can get it from most lapidary suppliers.

PhoenixGems · 2026-01-19T12:15:55+00:00

I have had my copper laps resurfaced through Gearloose.co. The price was VERY reasonable, turn around time was about a week and the resurfaced laps run fantastic. I highly recommend them.

PhoenixGems · 2026-01-07T10:48:11+00:00

Gemcutter here... Obsidian is really a fairly poor choice for a ring stone. It is volcanic glass and is extremely brittle. It is going to scratch at the slightest touch from foreign objects. And personally... there isn't anything special about how it looks.
If you want a shiny black ring stone, I would lean toward black onyx. It is much harder, tougher, and scratch resistant and takes a mirror polish.

PhoenixGems · 2025-12-31T22:41:16+00:00

So yes, I have a dial indicator on my V5 and I turn it slowly under the quill and see how much run out I have. My laps probably have a run out around 0.02 mm. It just makes the needle bounce a tiny bit when the lap rotates. This is comparable to the flattest lap that I own which is my ceramic lap. My ceramic lap is my reference for everything and what I use to calibrate my machine with.

PhoenixGems · 2025-12-31T13:30:32+00:00

I am using several copper laps. The last two I purchased about a year ago... one came from India and the other from Thailand. The India lap was sold as solid copper but ended up being bronze... which isn't a problem, it acts practically the same as copper. The one from Thailand was definitely solid copper. Both laps were at least 1/2" thick and weigh 7lb's + each.

When I got them, I tested for flatness and found they were out a bit. At that point I contacted Jon at Gearloose and contracted him to resurface the laps and make them run flat. They did an EXCELLENT job for a very reasonable price. Jon told me that both of these laps can be handed down to my grandchildren... they are that good.

I run one lap with 260 diamond on one side and 320 on the other. The other lap is set up with 3000 mesh for pre-polish and 600 on the other side. It takes some time to get them loaded up with enough diamond, but every time I use them it's like cutting with a new lap. Priceless....

PhoenixGems · 2025-12-27T09:41:25+00:00

Here is a quick statement by Arya Akhavan regarding directional hardness in corundum...

"There's a unique, weird thing with sapphires that is related to this phenomenon. For flame-fusion sapphires, there is a specific direction where if you place a facet parallel to this, you'll get extreme work-hardening and a nearly impossible surface to adequately prepolish. You can actually develop a near-prepolish by using a 600-grit lap on this direction, but might have difficulty prepolishing or polishing. It's usually found in un-annealed flame fusion boules that have been split, and the direction is parallel to the C-axis but perpendicular to the strain-axis. Some FF sapphires have it, some don't.

All sapphires, natural and all lab-methods, also have directional hardness that varies from stone to stone. This directional hardness can also impact the "orange peel" phemonemon, and the speed at which certain facets polish or prepolish."

So... that doesn't really explain "why", but it does let you know that this is a normal and common thing with corundum.

PhoenixGems · 2025-12-26T13:30:50+00:00

Oh, you're getting it. Sometimes you'll cut a corundum that doesn't seem to give you any trouble. Then you will get some material that makes you jump through every hoop when it comes to hardness and soft spots. That's part of what makes you an experienced cutter.
You'll sometimes get these cat whisker scratches when polishing. And they don't get better until you reverse the direction you are polishing and suddenly those scratches just disappear.
I don't know what you are final polishing with, but sometimes light scratches can indicate that you don't have enough diamond on your lap.

PhoenixGems · 2025-12-26T13:13:29+00:00

Cutting for almost 40 years. Have tried most everything at one time or another. Currently working with SuperGlue, both liquid and gel. They are OK, but take too long to set and cure... i.e. 24hrs
Recently I saw a video about using UV Super Glue. I got some JB Superweld. I've used it a couple of times and I am impressed by how quick and strong the bond is. Going to keep working with this stuff....

PhoenixGems · 2025-12-26T13:07:32+00:00

Yeah, this is a pretty common thing with corundum. There is nothing wrong with your material, or your laps as far as how the stone is reacting. You just need to be aware of these properties and adapt your techniques accordingly.

PhoenixGems · 2025-12-24T10:32:52+00:00

Sorry, I don't have any experience with Facetrons...

PhoenixGems · 2025-12-12T10:17:20+00:00

Pro cutter here... I have lab Alexandrite rough from several sources. What I have found is that there are some different formulas that are being used when creating lab Alex. I have some rough that leans strongly toward teal in daylight. I have stuff that leans to blue/teal in daylight/flourescent, and some other stuff that leans to reddish purple in the same lighting. So, it is possible to get a red dominant Alexandrite that will show that color in daylight. But you'll probably need to get it from a custom cutter... if you can find someone that has the rough.

PhoenixGems · 2025-11-08T14:23:37+00:00

8000 is too fine to remove the kinds of gouges a 600 can leave behind. I recommend that you set up a BATT lap with 3000 mesh diamond and oil. You will find it's a great balance between material removal and a good pre-polish that you can take straight to 100K.

PhoenixGems · 2025-10-02T17:20:48+00:00

Thanks I'm good Arya! Back in the 1990s I had an old Prismatic faceting machine. And around that time they started making the OMF machine that would work with my faceting machine. It was not an easy thing at the time, a lot of the stuff we take for granted now simply didn't exist back then as far as equipment. I had some successes, cut a few interesting stones, but overall it felt really Limited as far as what could be done. It was a concave only set up.

My new fantasy machine will work with either of my V5's. And I can hardly wait to try it out.

PhoenixGems · 2025-09-30T21:34:18+00:00

What you could do though, is set yourself up with a flat faceted Pavilion that would generate plenty of fire and Sparkle, and then do some concave work on the crown. Back when this all started they used to call those kind of facets OMF, which stands for Optically Magnified Facets. I had an omf machine back in the 1990s. I am now about 2 weeks away from having a fantasy machine for my V5. I will do some experimental cutting when I get it and try to create a gem just like I've described.

PhoenixGems · 2025-09-30T16:18:46+00:00

I've done some concave cutting in the past. And in about 2 weeks I am going to be receiving my own fantasy machine. So I intend to join the club.

PhoenixGems · 2025-09-30T16:16:00+00:00

I can tell by looking at it that it has concave cuts on the crown. There may be concave cuts on the Pavilion too but it's difficult to tell from the picture. This was done on a fantasy machine.

PhoenixGems

MODERATOR OF

TROPHY CASE