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How to Cut Tourmaline

Tourmaline is known as the "jester" of gemstones because of its many color variations. This color often varies along the c-axis (along the length of the crystal), but the perpendicular a/b-axes are always identical due to the crystal geometry. When the crystal is long with a dense c-axis, a rectangular shape with steep ends is best. In general, cutting the gem with a protruding c-axis will take advantage of the the color blending possible with this stone.

Things You'll Need

Gem saw
Protractor
Gem grinder
Gem lapping machine

Instructions

- 1
  Cut the rough form of the gem with a gem saw, which is a saw with a circular blade inset with diamond grit. It rotates at a high speed and a mechanism sprays water or oil onto the blade to keep it from overheating. Use a dop stick to hold the stone; if you must hold it by hand, use extreme caution.
- 2
  Set the angles of the facets with a protractor and shape the rough form with a grinder, a machine that uses wheels made of silicon carbide or impregnated with diamond grit, to create the pre-form. Use successively finer grit wheels to smooth the facets.
- 3
  Use the grinder to sand the gem with a sanding wheel, a very fine-grit grinder to remove any scratches left by the grinding process.
- 4
  Lap the facets of the stone with a lapper, a machine that resembles a disk sander. Use progressively finer disks to flatten the facets in preparation for polishing.
- 5
  Set a polishing disk on the lapping machine and polish the facets of the stone to a mirror-like finish. Set the stone on the lap for 3 seconds and then examine it to make sure the entire facet has been polished. If the polishing is uneven, adjust the lap accordingly using the cheater controls on the lap machine. Then polish the facets, checking your progress every 3 to 5 seconds.

Gemology