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 Black and gold make a beautiful and elegant combination. A black onyx ring is a perfect accessory for any outfit.