Inspect the rough stone by wetting with water under a bright light. Direct light is ideal. (The stone is fragile so hold it over a padded surface). Observe the depth and location of color layers. The gem material (fire layer) is usually covered by chalcedony. Trim away excess chalcedony by sawing, grinding, or sanding. Sawing should be used only for the top portion of chalcedony, which has no color. Leave 1/8 inch for grinding. For grinding use a 100-grit wheel. Grind not more than four or five seconds. Stop and examine for signs of fire under bright light. Shape the stone in any direction the fire indicates. Do not overheat the stone. Remember grind slowly and inspect often!
When you are satisfied that you have exposed all the fire, grind on a 600-grit wheel to eliminate scratches. Using a drumel, start with 325 diamond paste, moving to 600, then 1200, 3000, and finally 50,000. Remember: In all of the above steps of grinding, use plenty of water. Do not overheat.
Source: Rockonteur 6/05,
via Chips 12/05, via
Gneiss Times 2/06,
via Strata Gem 5/06
