OPAL: Birthstone for October

Opal in the Rough

Birthstones are always a tricky subject around here because the question of “who made up these rules anyway?” invariably comes up. Sure enough it’s a tough one to answer. Some say birthstones originated from ceremonial breast plates worn by high priests of the Ancient Israelites (called a ‘Hoshen’), which bore 12 different gemstones to represent the 12 distinct tribes of Isreal. We can take an inferential leap and see how 12 tribes could translate into 12 months over the ages, and it might be easy to stop here. But Greeks had birthstones too – not to mention Hindus, whose ayurvedic tradition is rich with astrological and therapeutic beliefs to this day. The truth is, much of what we think we know about birthstones in the Western world could all just be from a  pamphlet from Tiffany & Co published in 1870, which ostensibly leveraged the intrigue and facts about birthstones as more of an advertisement.

Nonetheless, the precious gemstone opal has been associated in one way or another with the month of October throughout references and literature for over 500 years. It was once thought the most valuable of all gems, as its flashes of color and iridescent hue had many believing it was actually a combination of all precious stones in one. Today opal is still an especially treasured gem, with top-quality black opal in particular fetching over $2000 per carat. So if you were born in the month of October, put loved ones on notice to get their pocket books ready; opal can be as pricy as it is beautiful.


A Wild Variety

Opal is found in a stunning array of shapes, sizes and colors from all over the world. Australia, however, claims opal more or less as its own. It’s the national gemstone, as the country produces over 90% of the world’s supply. Its black opal (especially those found on Lightning Ridge) holds the distinction as the most prized specimen on the planet. In a close second place for value and rarity is the bolder opal – cut from ironstone boulders that are its namesake. Bolder opals demonstrate an equally vibrant play of color, if only because portions of ironstone must be left on the gem to achieve it. White opal is more common but rarer still than other gems and offers a delicate sparkle of colors, not unlike that of a jellyfish.

From left to right, top to bottom: 1.62ct oval white opal, 1.66ct long oval boulder opal, 1.08ct round Lightning Ridge black opal, 1.38 pear white opal

A Gem of Water

If at first glance opal may seem almost fluid in nature, and you’d actually be correct: Unlike any other gemstone, opal is comprised of 3-20% water. The rest is microscopic spheres of silica, formed over eons of wet and dry spells in the ground. The dry, arid regions of the world where opals are found lend a clue as to their ideal environment. Opals are formed in cracks and fissures in the earth where traces of silica are pushed down with swelling rain water, left to slosh around atop the water table, and dry out over the predominately dry season. This cycle repeats over a million years until amorphous veins of minable opal are formed.


A Play of Color

Gaze at an opal from different angles and you’ll surely find it glimmers with changing color. How is that happening? It all has to do with diffraction, the phenomenon when light rays backscatter upon encountering obstacles or slits in matter. Those tiny spheres of silica that comprise opal all join together – but just like a jar of marbles – they leave tiny gaps in between them. Just as mist diffracts light to produce a rainbow in the sky, we perceive opal’s vibrant colors from its ‘play’ on the light bouncing back through little gaps in its make up.

Caption: The same opal viewed from different angles and in different light can appear vastly different.

Opal Jewelry

Much of the finished opal jewelry for sale in the world is in the form of pendants, not rings. Opal is an especially soft and brittle gem easily susceptible to breakage. A piece worn around the neck is far more protected from the kind of wear and tear endured by pieces worn on the hand. This doesn’t mean opal isn’t a great candidate to be incorporated as the center piece of a ring – it is (Green Lake crafts new opal rings every month) – but the setting for an opal must be chosen very carefully. Because soft opals are sure to be abraded if worn in a ring, it’s important the thinnest area (e.g. the edges) be incased in metal. This can be done by designing in a full or half bezel for gems to be set, employing a wider wrap style setting or even grinding and polishing the opal as an inlay. Here are a few recent examples:

Custom Made 14K White Gold Diamond Ring with White Opals

This wider ring is lightened by intricate pierced work and is low-set so as not to catch or snag. Full bezels are incorporated into the curls to better ensure opals aren’t cracked or chipped.

See this ring in detail on the Green Lake Client Gallery

Platinum and Diamond Wrap Ring with Lightning Ridge Opal Cabochon Center

Not entirely a full bezel, this wide wrap setting protects its precious center from the majority of snafus typically encountered in wedding jewelry (e.g., falling off the bathroom sink, fishing for car keys, etc.).

See this ring in detail on the Green Lake Client Gallery


White Gold Wedding Set with Marquis Diamond Center and Bolder Opal Inlay

By cutting opal in-house Green Lake has been able to do some pretty cool custom inlays. This ring, with its fluid wave-like contours really makes use of the opal’s shimmering iridescence.

See this ring in detail on the Green Lake Client Gallery


Warm White Gold Halo Setting with Faceted Ethiopian Opal Center

Opal richer in crystal with minimal water content is able to be faceted like a diamond. The ideal setting is still a bezel (or for this ring, a halo with a hidden ring of diamonds along the side).

See this ring in detail on the Green Lake Client Gallery

The Fire Opal

The vivacious and bright orange flare of a fire opal is not what we typically associate with this gem variety, yet they are indeed related. Found in dryer regions of the world the fire opal lacks the water found in its white opal cousins, making it a more durable gem with consistent clarity, seeming almost ‘jelly’ like. Much of fire opal is presently mined from Mexico, where it’s also the nation’s official gemstone.

1.69ct emerald cut fire opal

Opal Art

When Italian gemologist and faceter Daniela L’Abbate moved to Australia in the early 90’s she developed entirely new carving techniques, freeing the gem from the rough while respecting its natural shape. The results of her approach are truly stunning, revealing in opal surrealistic forms with unrivaled play of color. Here are a few of our favorite works we wanted to mention:


From a rough piece of Lightning Ridge opal, sand is removed and the gem is shaped to optimize its natural contours. After some 18 hours of polishing with a specialized diamond paste, an impressive 90 carats of gleaming opal appears almost like a wispy ghost.

Wraith Opal

Jasmine Coral Opal

Lightening Ridge rough transformed into the delicate representation of jasmine coral.

jasmine Coral

An American Opal Field

Did you know the virgin valley in Nevada has an amazing array of all these varieties, from precious black opal to crystal, white, fire and lemon opal? In fact, the black fire opal is the official gemstone of Nevada. The largest black opal in the Smithsonian institution known as the “Roeabling Opal” came out of the rainbow ridge mine in 1917 and weighs a whopping 2585 carats!


Interested in seeing the Green Lake opal collection or having opal custom cut? Contact gemstones@greenlakejewelry.com

For inquires on creating a custom opal ring and pricing Start a Design Page and contact a designer today.

Written and illustrated by Eric Robertson / Photography for Green Lake Jewelry Works by Margaret Page & Edwin Lawrence III 
Additional photo credit: Opal Carvings by Daniela L’Abbate / ‘Fox Coral’ by R Tebben 
About the author: Eric Robertson is a writer, illustrator and creative lead for Green Lake Jewelry Works.