October has arrived, and as well as the promise of crisper days, roast dinners and Halloween treats, there is another reason to delight – it’s opal month. For anyone celebrating a birthday in October, this is your kaleidoscopic birthstone.

The shape-shifting opal is unlike any other gemstone; its flashes of rainbow-hued light do not need the encouragement of a cutter’s tool to dance and sparkle. It will be left as a smooth stone, most often a bulbous round or oval, but also works well in organic, irregular shapes.

While the Bedouins might have believed that opals were filled with lightening, and it’s easy to see why, it is another natural element that gives them their bewitching play of colour – rain. Opal’s play of colour is created by water trapped within the gemstone’s silica structure (up to 20% of an opal is water). Millions of years ago, when arid lands – such as the Australian Outback, which is well known for its opals – were drenched with rain, the water pushed deep into rocks, dragging down a silicone compound. This combination of geological factors led to the creation of this shimmering stone.

There are many kinds of opal, the best known being white opals and black opals. White opals pepper their namesake colour with flashes of rainbow – the best examples are Welo opals found in Ethiopia. Black opals, the rarer of the two, offer an even stronger play of light with a storm of reds, oranges, purples and blues against a moody, dark background – ask for Lightening Ridge opal from Australia for the finest example of this.

Mexican fire opals are a strong flaming orange, often displaying strong flashes of yellow and green. These energising stones – some of which don’t display the hypnotic rainbow effect, yet are still prized for their strength of colour – get their shade from traces of iron oxide. The volcanic glow they emit is believed to inspire courage and stamina.

Pink opals are another variety that don’t always have a play of colour – and are often the better for it. Soft pink opal, mostly hailing from Peru, is a beautifully feminine shade, and looks wonderful next to other pastel gemstones, like chalcedony, and warm rose gold.

For all opal’s many delights, it does have a chequered history. It was long considered to be an unlucky stone, most probably because its delicacy would have led to some expensive errors on the cutting bench. However, for those who believe in the healing power of gemstones, this particular stone is said to encourage freedom and independence, stimulate originality and creativity, and release anger while helping you to find your true self.

Ten October birthstone opal jewels…

1

Drutis 18ct white gold Solomon’s ring with. moving opals, £2,700

2

Anne Sisteron 14ct yellow gold, diamond,  emerald and opal Oblong earrings, $5,500

3

Retrouvaí 14ct yellow gold, diamond, tanzanite and Australian opal inlay Truth pendant, $4,180

4

Nana Fink 18ct rose gold and hand-carved Andean pink opal Sophistiquee Ring. No. 1, CHF5,800

5

Andrey Yarden 18ct yellow gold, amethyst, sapphire and Australian opal Bohème earring, $4,500

6

Jessica Steele gold-plated silver and opal Disc necklace, £55

7

Katherine Jetter 20ct yellow gold, violet sapphire, tsavorite garnet and boulder opal Cubed Corner ring, $66,000

8

Sorrel Bay 18ct recycled gold and bi-colour opal Lines Droplets earrings, £2,300

9

Brent Neale 18ct yellow gold, diamond, pink tourmaline, citrine, blue topaz and opal Medium Rainbow ring, $8,225

10

Robinson Pelham 9ct yellow gold, pink sapphire and pink opal Siren earrings, £6,900 

All prices were correct on the date of publishing, but may be subject to change