Opal’s characteristic “play-of-color” was explained in the 1960s, when scientists discovered that it’s composed of microscopic silica spheres that diffract light to display various colors of the rainbow. These flashy gemstones are called “precious opals.” Those without play-of-color are “common opals.”
Dozens of opal varieties exist, but only a few, such as fire opal and boulder opal, are universally recognized. Opals are often referred to by their background “body color” of black or white.
Opal’s classic country of origin is Australia, but Opal is also mined in Mexico, Brazil, Honduras, Ethiopia, the Czech Republic, and parts of the U.S., including Nevada and Idaho.
Wearing opal jewelry is well worth the extra care, though. This October birthstone has remained a popular choice for centuries.
Tourmaline is not one mineral, but a fairly complex group of minerals with different chemical compositions and physical properties. Certain trace elements produce distinct colors, and many resulting varieties have their own names.
Tourmaline is mined in Brazil, Sri Lanka, Nigeria, Mozambique, Madagascar, Afghanistan, Pakistan and the U.S.—primarily Maine and California.