It is often cut into cabochons that display a patch of fire or precious opal surrounded by rhyolite. This opal is known as "cantera" but it also fits the definition of boulder opal.ADVERTISEMENT Honduras is known for its boulder opal and matrix opal found in andesite and basalt host rock....
Sometimes fire opals that do not display color play are referred to as jelly opals. Occasionally Mexican opals are cut into their rhyolitic host material if slicing and polishing is difficult enough. A form of opal from Mexico is called an opal from Cantera. A type of opal from Mexico, know...