OPAL - 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.
TOURMALINE - Its name 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.
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.”
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 opalised fossils.
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 is the alternate birthstone for October, along with the opal. The stone was first discovered by Dutch traders off the West Coast of Italy in the late 1600's or early 1700's.
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.