Fire Agate is an iridescent brown form of chalcedony. The polychromatic glow emanating from this stone results from internal layers of limonite. The deep red and orange flashes resemble glowing hot coals. The play-of-color can also present green and blue bursts in seductively vivid hues. The least desirable specimens are brownish in tone. The color play can arrange itself in any number of patterns, some more pleasing than others, but consistency throughout is the key to desirable gems.

Careful cutting to follow the stone’s curvature leaves the lapidary with irregularly shaped examples. These oddly shaped stones are tricky for jewelers to set. In addition, the finished examples usually have a very uneven surface with an almost bubble-like appearance. Most cut and polished fire agates are set in one-of-a-kind jewelry created by artisan jewelers.

Despite the drawbacks, fire agates can be incredibly beautiful treasures. More resilient than the ever-popular opal, it’s surprising we don’t see more examples in fine jewelry.