Boulder opal is a member of the opal family. It has a dark base surface with an exciting play of color. On Mohs¡¯ scale of hardness, boulder opal is 1.98-2.50. Its primary sources include Australia, Brazil, Guatemala, Honduras, Indonesia, Japan, Mexico, Russia, Nevada, and Idaho.

 

Color

 

Boulder opal has a dark base surface with an exciting play of color.