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Question: I’ve learned something from cutting tourmaline gemstones. Sometimes they just shatter. What I can’t figure out is what makes some tourmalines so unstable. I use a cold dopping process. I do my best to carefully remove material in a way that doesn’t put too much “stress” on the crystal. Still, I lose a good number of big, blocky pieces. Sometimes, the entire crystal suddenly just fills itself with fractures. Then it goes on the great journey to my fish tank. I seem to have trouble especially with African tourmalines, particularly lighter pink ones. I’ve also given up using a 260 grit lap on them. (Even seemingly tougher Afghan tourmalines grow fractures when I use a 260). I think this might be due to a weird ringing sound.
By International Gem Society 2 minute read
pink tourmaline

Pink tourmaline, photo by Tiffa Day. Licensed under CC By 2.0. (Cropped to show detail).

Answer: Tourmalines can pose challenges, even for experienced faceters. Your choice of lap and facet progression can play a critical role in whether or not your stone will shatter.

Selecting the Right Lap

I have a friend who facets both nodules and crystals of tourmaline. I shared your question with him. He’s had no problem cutting tourmaline nodules. However, he has experienced the same problem you described, only with Nigerian green tourmaline crystals. He had preformed them with 260 grit diamond. My friend solved the problem by not touching the crystals, during preforming or cutting, with any courser grit than a 1200 flat lap. He said it’s slower, but you won’t end up with a bunch of aquarium gravel.

Hope this helps,

Doug

Cutting Tourmaline Facets in a Safe Progression

I have some tips for cutting tourmaline gemstones that might reduce their likelihood of shattering.

Never cut the girdle first. Try to cut as much of the pavilion as possible, while leaving the crystal faces as intact as you can, before establishing a girdle. These natural surfaces serve to hold the crystal together. Removing them prematurely could cause the crystal to lose integrity.

facets - advice for cutting tourmaline

Two other issues to be aware of are heat sensitivity and the coarseness of the cutting lap. (I dop with a small amount of epoxy for initial dopping). Don’t use anything coarser than a 600 grit.

I do think the 260 grit is the ultimate tourmaline killer. It probably does have something to do with sonic vibration. I’ve had no problem with Afghan tourmalines until I used the 260. It does make an odd ringy sound.

Hope this helps eliminate your cutting tourmaline woes.

Daniel

silver brooch with tourmaline

Cast and soldered silver cube brooch by Chris Boland, set with a green tourmaline. Photo by Design Initiative. Licensed under CC By-SA 2.0.