THE BIRTHSTONES OF OCTOBER: OPAL AND TOURMALINE
October is unique among the months as it has not one, but two birthstones: opal and tourmaline.
Why does October have two birthstones?
The tradition of assigning multiple birthstones to a single month dates back to ancient times, allowing for more variety and accessibility. In modern times, this tradition has been embraced to offer options that suit different tastes and budgets. October's birthstones, opal and tourmaline, each bring unique qualities and colours to the table.
What is an opal?
Opal is a mineraloid known for its unique play-of-colour. Unlike other gemstones, opal displays a rainbow-like iridescence that changes with the angle of light. This phenomenon, called ‘opalescence’, is caused by the diffraction of light within the stone's microstructure.
What is tourmaline?
Tourmaline is a crystalline boron silicate mineral compounded with various elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. This diverse composition results in tourmaline's wide range of colours and makes it a highly sought-after gemstone.
Where are opals found?
The majority of the world's opals are mined in Australia, which produces over 90% of global supply. Notable opal fields are located in Coober Pedy, Lightning Ridge, and Andamooka. Opals are also found in Brazil, Mexico, and Ethiopia, each location producing opals with distinct characteristics.
Where is tourmaline found?
Tourmaline deposits are found worldwide, with significant sources in Brazil, Afghanistan, Pakistan, Africa (especially Mozambique and Nigeria), and the United States (California and Maine). Brazil is known for producing the highly prized Paraiba tourmaline, renowned for its vivid blue to green hues.
History of opals
Opals have been treasured since ancient times. The Romans considered opals a symbol of purity and hope, while the ancient Greeks believed opals gave their owners the gift of prophecy. In the Middle Ages, opals were thought to bring good luck. Opals have also been associated with numerous superstitions, both good and bad, throughout history.
History of tourmaline
Tourmaline has been known for centuries, but it wasn't until the 19th century that it was recognised as a distinct mineral species. Ancient Egyptians believed tourmaline travelled along a rainbow on its way up from the centre of the Earth, which is why it has such a wide range of colours. Tourmaline was often mistaken for other gemstones until its unique properties were better understood.
What is rarer - opal or tourmaline?
The rarity of opal versus tourmaline depends on the type and quality of the gemstone. High-quality black opals from Lightning Ridge are exceptionally rare and valuable. On the other hand, the rarest tourmalines, such as the neon-blue Paraiba variety, are also incredibly scarce and can command high prices.
Colours of opals
Opals come in a spectrum of colours, including white, black, blue, green, red, yellow, and orange. The most prized opals exhibit a play-of-colour, with black opals being the most valuable due to their dark body tone which enhances the vibrant colours within.
Colours of tourmaline
Tourmaline is known for its incredible colour variety, including green (verdelite), pink (rubellite), blue (indicolite), and the unique neon blue-green of Paraíba tourmaline. Some tourmalines display multiple colours in a single crystal, known as watermelon tourmaline, which exhibits green, pink, and white zones.
Opals and tourmaline in jewellery design
Both opals and tourmaline are popular choices for jewellery due to their striking appearance and range of colours. Opals are often set in rings, earrings, and pendants, making use of their play-of-colour to create eye-catching pieces. Tourmaline's durability and colour variety make it ideal for all types of jewellery, from statement rings to delicate necklaces.