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How to Polish a Rough Fire Agate

Fire agate, also known as "cinnamon opal" or "opalescent agate" due to its color radiance, is a mysterious stone whose fire-like brilliance is revealed through cutting or grinding away its milky-to-grayish chalcedony surface. Fire agate specimens are bubbly in appearance and require a skilled lapidarist, or stone-shaping professional or hobbyist, to grind, sand and polish each "bubble" until the most colorful layers appear. Finely cut and polished fire agates often appear in jewelry and mosaics, due to their hardness and durability. They can also be shaped into flat slabs or dome-shaped cabochons.

Things You'll Need

Stone faceting or cabbing machine
Sanding tools
Specialized saws
Polishing agent

Instructions

- 1
  Set up the lapidary or stone-cutting equipment. Proper types of equipment include stone faceting machines, cabochon or "cabbing" machines, specialized saws and sanding tools. Due to the hardness of the exterior chalcedony layer, use diamond grit grinding wheels traditionally used to cut diamonds.
- 2
  Grind or saw away the chalcedony layer thoroughly and carefully. You may also need to grind away additional layers of brown or grayish agate to reveal the most colorful, "fiery" layer. When grinding the first layer, use particular caution to prevent chipping or damaging the layers beneath.
- 3
  Shape the stone into your desired form. Use specialized lapidary grinding wheels or saws to maintain a smooth bubbly appearance or to slice the stone into slabs. Use a cabbing machine to form a cabochon shape. While shaping, gradually replace coarser grinding wheels with finer wheels. Sand the finished stones to achieve a smooth texture for polishing.
- 4
  Polish the stone using the appropriate polishing agent to reveal its iridescence. Tin or cerium oxide is most often recommended for fire agates.

Rocks & Minerals