Mexico is of course, the main source of the Mexican fire opal. Very highly prized Mexican fire opals are excavated in open-cast mines in Queretaro, Mexico. However, the stone can also be found in Guatemala, Honduras, the United States, and Australia, where more precious varieties are known to be found. Germany has been importing most of Mexico’s best fire opals for many decades now.
Fire opals are extremely fragile, and suffer from changes in humidity, temperature, and even light. However, with the proper care, your fire opal can last a long time. Opals contain as much as 20% water, which means they can get very dry and wind up cracking. This phenomenon is called “Crazing,” and may be avoided by soaking your opal in water for a few hours, occasionally. Some opals are actually filled with oil, wax, or plastic, to avoid crazing. It is important that opals never be touched with any oils or chemicals. It is also important to protect your stone from any blows or scratches.