Fire Opal engagement rings? Absolutely! Diamonds may be a girl's best friend, but Fire Opal engagement rings are a unique, original, and a far more affordable choice. This birthstone of October embodies the orange and red colors of a warming fire. The fiery sparkle of this gem makes a fire opal ring become the center of conversation The birthstone of December, the intense deep blue color of a london blue topaz ring can evoke thoughts of warm Caribbean nights.