Opal is October’s Birthstone

Opal is the official birthstone for the month of October.  It is derived from the Sanskrit word “upala”, meaning valuable stone.  The discovery of opals is ancient and uncertain.  It is believed that opals were first mined around 400 BC in Ethiopia but their popularity didn’t grow until around 100 BC when they were mined in Hungary.  Precious opals were discovered in South Australia, Queensland, and New South Wales, Australia in 1887.  Australia is now the world’s primary source of precious opals.  There is an old idea that opals are bad luck but Queen Victoria’s love of opals restored their popularity.

Opal is an amorphous form of silica related to quartz, a mineraloid form, not a mineral. Opals are unique stones that come in a variety of colors, as well as rainbows of color in one stone. Most precious opals have a white or nearly colorless base and, in wonderful cases, exhibit sparkles of color known as play-of-color. Black opals actually have a dark blue or blue-green base, and opals known as semi-black can have a grayish, bluish, or greenish base. Opal ranks a 5.5-6 on Mohs’ hardness scale. 

Opals should be protected from chemicals, high heat, prolonged direct sunlight, and any kind of oil or grease.  Because opals are 5 to 10 percent water, it is natural they might dry out and craze (small hairline cracks) after a lifetime set in a piece of jewelry.  They should not be stored in dry, air-tight containers like safe-deposit boxes, and it couldn’t hurt to soak an opal in pure water from time to time.  Opal jewelry should be cleaned with mild soapy water and a soft brush or cloth.