OCTOBER: OPAL & TOURMALINE
The name “opal” originates from the Greek word opallios, which meant “to see a change in colour.” The Roman scholar Pliny used the word opalus when he wrote about this gemstone’s kaleidoscopic “play” of rainbow colours that could simulate shades of any stone.
Opal’s characteristic “play-of-colour” was explained in the 1960s, when scientists discovered that it’s composed of microscopic silica spheres that diffract light to display various colours of the rainbow. These flashy gemstones are called “precious opals;” those without play-of-colour are “common opals.”
Dozens of opal varieties exist, but only a few (like Fire Opal and Boulder Opal) are universally recognised. Opals are often referred to by their background “body colour”—black or white.
Opal’s classic country of origin is Australia. Seasonal rains soaked the parched Outback, carrying silica deposits underground into cracks between layers of rock. When the water evaporated, these deposits formed opal. Sometimes, silica seeped into spaces around wood, seashells and skeletons, resulting in opalized fossils.
Since opal was discovered in Australia around 1850, the country has produced 95 percent of the world’s supply. Opal is also mined in Mexico, Brazil, Honduras, Ethiopia, the Czech Republic and parts of the U.S., including Nevada and Idaho.
The water content of opal gems can range from three to 21 percent—usually between 6 and 10 in gem-quality material. This, combined with hardness of only 5.5 to 6 on the Mohs scale, makes opal a delicate gemstone that can crack or “craze” under extreme temperature, dehydration, or direct light.
Wearing opal jewellery is well worth the extra care, though. For centuries, people have associated this precious gemstone with good luck. Though some modern superstitions claim that opals can be bad luck to anyone not born in October, this birthstone remains a popular choice.
Tourmaline comes from the Sinhalese word ‘Toramalli’, which means ‘stone with mixed colours’ because of the array of colours that are present in one crystal. The most popular colour variations are pink, red, green, and blue to violet Tourmaline. Tourmaline is also known for being bi and even tri-coloured. A popular bi-coloured type is Watermelon Tourmaline, which displays pink, white and green colour bands.
Because of how many colours of Tourmaline there are, it has often been mistaken for other gemstones like Ruby and Emerald. These misidentifications went on until the 1800s when it was discovered that Tourmalines had a unique mineral composition.
This October birthstone is most commonly found in Brazil. However, it has also been mined in Kenya, Mozambique and Madagascar, as well as other countries in Africa.
Tourmaline is a fairly tough gem, sitting at a 7 to 7.5 on the Mohs scale of hardness. This makes it a good choice for everyday wear. Tourmaline is best cleaned in warm, soapy water with a brush with soft bristles. Ultrasonic and steam cleaners should not be used on Tourmalines.