Opal

Opal is the world’s most popular phenomenal gem, displaying most of the time an intense play of colors. Many cultures have credited opal with supernatural origins and powers.
Experts divide gem opals into many different categories, with the main four being the white opal (found in Australia and Brazil), the black opal (found in Australia) and the fire opal (found in Mexico).
Opal is one of the birthstones for October.