Fire opal is considered the national gemstone of Mexico. It comes in transparent shades of red, orange, and yellow with bright color flashes. Fire opals form in Mexican volcanoes when water seeps into lava and fills hollows, combining with silica to create a solid gel. They are rare as only some develop the brilliant color flashes, while others are transparent or translucent. Engagement rings featuring fire opals are unusual and meaningful as the stone is formed purely by nature. Protective settings are recommended due to the opal's softness and water content.