DescriptionOpal is an amorphous form of silica, so technically it is a “mineraloid” rather than a “mineral,” with has to have a crystal structure. It is the October birthstone. The colors come from diffraction of light off of internal flaws.There are many spots in the world that have been renowned for millennia for their interesting mineral specimens.Over the decades I’ve been selling collectibles my market has been about 97% coins, 2% paper money, 1% everything else.
