Opal Specialist Mini Course
Opal Engagement Rings
Purchase Opal Specialist Mini CourseAttention all opal lovers! If you have found yourself mesmerized by the changing color patterns of this mineraloid, you'll love this course. Do a deep dive into the properties of opals to discover how they are formed and reflect light. Looking to purchase or sell an opal? Learn about different types of opals and how to properly care for them. Every opal enthusiast will learn something new in this course.
What is an Opal?
Opals are made of microscopic spheres of silica and typically contain 3 to 10% water. If those spheres have uniform sizes and shapes, the opals will display the famous play of colors that makes these stones unique. These are called "precious opals." However, only 5% of all opals meet this criteria. The rest are called "common opals." While they may occur in many beautiful colors, common opals are less popular as jewelry stones.
Australia produces 96% of the world's opals from sites such as Lightning Ridge, Coober Pedy, and Queensland. Other notable sources include Brazil, Ethiopia, Mexico, and the United States.
Precious opals have multi-colored flashes that move across their surface as well as vibrant body colors. Some even show colorful patterns that have received descriptive names like harlequin, fern leaf, peacock, and rolling fire. These opals just have an ethereal, otherworldly appearance. In the mythologies of many different cultures, opals come from the heavens.
Are Opals Unlucky?
Although the traditional October birthstone is available in jewelry stores everywhere, opal has a reputation for bad luck. This may be a modern twist on opal folklore. An early 19th century novel by Sir Walter Scott may have contributed to the popular association between opals and misfortune. Nevertheless, despite the rumors, opals remain very popular.
How Fragile are Opals?
Opal's composition does make it more susceptible to damage than most other popular jewelry stones. Unfortunately, these sensitivities may reinforce the perception that opals are unlucky. With a Mohs hardness of 5 to 6.5, opal is even softer than household dust (7). Therefore, roughly brushing dust off an opal may scratch its surface and start to dull its polish. Impacts can also break opals, and their high water content makes them liable to crack and even shatter due to sudden temperature changes.
If you're considering buying an opal engagement ring, be aware that an opal is a delicate stone that needs special attention. Ultimately, this may be the overriding factor in your decision.
Opal Types and Value
Choosing an opal engagement ring does have some advantages. You can buy a beautiful, high-quality stone at a far more affordable price than a diamond, emerald, ruby, or sapphire. Since opals have a much lower specific gravity or density than these other gems, you can also get a much larger sized ring stone for the same carat weight.
There are many varieties of opal. The following are the most popular choices for ring stones.
Opals vary widely in price depending on their variety and quality. Black opals are the most prized. These gems have a black or dark blue background and show their play of color most vividly. Prices for fine to extra fine quality gems usually range from thousands to tens of thousands of dollars per carat. For a high-quality engagement ring-sized black opal (1-3 cts), expect to pay a few thousand dollars.
The second most valuable type of opal, crystal opals are transparent to semi-transparent. They look like bright drops of dew with rainbow hues floating in them. Prices for fine crystal opals can range from a few hundred to something in the low thousands of dollars.
Especially popular in the United States, white opals make up the bulk of commercial sales. They tend towards translucency and milky white, gray, or pale yellow backgrounds. Top-quality white opal should have an even, distinct pattern of color. Expect to pay a few hundred dollars for a decent quality white opal.
Boulder opal is mined with its host ironstone or sandstone still attached. This material actually reinforces the opal, which tends to be very thin. The host backing also has the advantage of darkening the background and increasing the opal's play of color.
Boulder opals tend to come in irregular sizes and are used in one-of-a-kind pieces.
Matrix opal is a closely related material. It has veins of opal mixed together with the host stone.
Boulder opal prices vary from tens to hundreds of dollars per carat. Most boulder opals will cost at most a few hundred dollars. A few extra-fine specimens, particularly Yowah nut opals, may cost more.
Sometimes called water opals, these gems tend to show semi-translucency but lack crystal opal's bright flashes of color. They often resemble moonstones. With prices ranging from tens to the low hundreds of dollars per carat, jelly opals are one of the most affordable opal varieties.
Fire opals have red, orange, or yellow backgrounds. The most valuable specimens have a fiery red or red-orange hue, uniform color, and no milkiness. (Milkiness in a fire opal often indicates the stone is drying out and about to crack).
While fire opals may often lack play of color, consumers still prize them for their beautiful hues. Their prices usually range from tens to the low hundreds of dollars per carat.
A Note on Opal Prices
These prices are rough estimates. Since each opal is unique and there are stunning specimens within each opal type, prices can vary widely. Couples looking for relatively affordable opal engagement ring stones with play of color should consider white or crystal opal varieties.
Quality Factors for Opal Engagement Ring Stones
Since opals are such unique gems, it should come as no surprise that they also have a unique grading system and terminology for appraisals. Our opal buying guide and appraisal guide cover these topics in more detail. When shopping for opal engagement ring stones, focus on these qualities.
Play of Color
Look for an opal that has intense and evenly distributed play of color across the stone.
The play-of-color pattern known as harlequin is the most highly valued. It consists of a patchwork of diamond-shaped flashes spread across the entire stone. The diamond shapes should be large.
White opals will often demonstrate pinfire, a series of bright, colorful dots.
Any play-of-color pattern that shows red is highly valued. When choosing an opal, pick it up and turn it in your hand. Look for a strong fire, especially red fire, all throughout the stone.
Choose an opal engagement ring stone with good shape appeal. Since most opals receive cabochon cuts, this usually means the stone should be symmetrical (not too slim or too wide if it's an oval) and have a smooth, full dome.
The dome helps build the color and fire of the stone, especially for paler opals. Therefore, make sure the dome isn't dented or pointed, unless the stone has been cut into a sugarloaf shape. (Sugarloaf cabochons have a raised point, like a cone, or a ridge, like a mountain). Usually, full domes appear more harmonious.
8 mm (1.96-ct) white opal cab in a delicate, wildflower-inspired white gold bridal set. Photos by CustomMade. Used with permission.
Thinner stones, especially white or crystal opals, may appear see-through if their fire isn't strong enough to reflect light back into the viewer's eyes. Thus, retail stores will often present opals on black velvet. If possible, ask to pick up these stones and place them in your hand. This will give you a better idea of how the opal will look against the hand in an open-back setting. Ideally, an opal's body color or play of color should be strong enough that the wearer's skin color isn't readily visible through the stone.
Avoid Cloudy Opals
Never buy opals sold in jars of water or that appear cloudy. Cloudiness may signify that a stone is dry and about to crack. Some merchants will sell their opals in jars of water if the stones come from a source known to produce opals with high water content. These stones have a greater tendency to crack or craze.
Money-Saving Options: Assembled and Synthetic Opals
For couples on a tight budget, assembled opals, either doublets or triplets, can make great engagement ring stone alternatives. These beautiful pieces can contain natural opal, and a clever setting can disguise their "assembly." Assembled opals may also have greater wearability than other opal jewelry stones.
For couples who want a black opal but can't afford a natural piece, synthetics offer a practical option. However, those who want white or crystal opals may prefer naturals to synthetics. The price difference between these natural opals and their synthetic counterparts may be too small to justify buying synthetics. In addition, you can usually tell the difference between natural and synthetic opals fairly easily.
What are Assembled Opals?
Opal doublets are thin layers of opals glued to ironstone, onyx, or some other backing, which may be made of natural or synthetic materials. Jewelers may create these pieces when an opal is too thin or fragile for jewelry use on its own.
Opal triplets differ from doublets in that the opal layer is sandwiched between a dark backing and a domed, top layer of clear quartz. Since quartz has greater hardness than opal, it protects the opal from scratches and also makes the cabochon look fuller. Usually, jewelers use even thinner opals for triplets than doublets.
How Can You Identify an Assembled Opal?
Most retailers will readily disclose whether or not an opal is assembled. Unfortunately, some may try to pass off an assembled opal as a solid, natural boulder opal. The key to distinguishing an assembled opal from a solid opal is to check between the opal layer and ironstone backing for a thin, sandy layer of brown glue that differs in texture from both the opal and the ironstone.
Triplets are usually easier to detect than doublets. Simply look at the stone from the side and see if the stone appears unusually clear and glassy. Triplets also won't demonstrate play of color from the side, while solid opals will. However, the quartz top layer of a triplet can make it harder to tell if the opal layer is actually natural or lab-created.
Anyone shopping for opals, especially pieces already set in jewelry, should be especially cautious about undisclosed assembled stones. The jewelry settings can make viewing the stones from the side difficult, thus making seams hard to detect. However, please keep in mind that there is nothing inherently dishonest about creating and selling assembled opals. As always, what is important is that customers know what they are buying.
Lab-made or synthetic opals closely resemble natural opals. They can have the same coloring and play of color, but their patterning appears different. The flashes of color within natural opals usually demonstrate "brushstrokes," while synthetic opals show a "snakeskin" pattern.
"Brushstrokes" Versus "Snakeskin"
Each flash of color within a natural opal should contain parallel streaks, as if the color was painted on with a paint brush. The streaks tend to run along the length of the flash of color, and each flash of color has a brushstroke oriented in its own direction.
In contrast, synthetic opals exhibit a sharp, scalloped, and scaly pattern, hence the term "snakeskin." (This is also sometimes called a "chicken wire" pattern). Another telltale sign of a synthetic opal is if the pattern of alternating colors appears too well defined and evenly spaced, and sometimes even a bit busy or choppy. If an opal appears psychedelically colorful and crisp in pattern but has a very low price, odds are it's synthetic.
Please note that some natural Welo Ethiopian opals may also have a snakeskin-like, "honeycomb" pattern.
Synthetic Columnar Color Structure
You can also tell if an opal is synthetic or natural by examining the sides of the stone. In natural opals, the brushstroke pattern continues down the sides. On the other hand, synthetic opals show a columnar color structure from the side. The colors look like rods or long, unbroken streaks running up the side. (Just imagine someone clutching a bunch of multi-colored pipe cleaners. You can see different spots of color from the top, the "snakeskin," and the lengths of different-colored pipe cleaners from the side, the columnar structure).
Synthetic Opals in Assembled Gems
Lab-created opals are starting to look more and more like the natural thing, but they're still detectable. However, the opals in doublets and triplets are usually too thin for columnar structure to be visible. Therefore, for assembled opals, identification depends entirely on recognizing the brushstroke or snakeskin pattern.
Should You Buy Synthetic or Natural Opal?
From a consumer perspective, again, as long as you know what you're buying, you can decide if you want a synthetic or natural opal engagement ring stone.
Settings for Opal Engagement Ring Stones
Opals are almost always cut into cabochons. Sometimes, gem cutters facet white and fire opals. Boulder and matrix opals can also be polished into a wide variety of shapes.
Custom-cut faceted white opal (1.05 ct round) in white gold dragon-themed split shank engagement ring. Photos by CustomMade. Used with permission.
Opals are most often cabbed into oval shapes, although rounds, teardrops, squares, rectangles and triangles are sometimes seen. If there is enough rough material, most opal cabochons are cut with high domes that allow light to travel through more of the stone. Thinner roughs are cut into flat shapes.
Jewelers usually set high-domed cabochons with prongs. This keeps the stone visible from the sides, so viewers can enjoy the opal from all angles.
Oval shapes require four prongs, while shapes like teardrops and triangles usually require three prongs, including at least one v-shaped prong to protect points from chipping.
For flatter opals, jewelers may use bezel settings that wrap around the entirety of the stone. This offers the opal greater protection from chipping. Jewelers also apply epoxy to the bezel (or prongs) to help the gem stay in place and prevent the metal from damaging the opal during the setting process. Oil is used to prevent the epoxy from sticking permanently to the opal, in case the owner wants to reset the opal in the future.
After choosing a setting type, you must decide next whether you want an open or closed back for the setting.
Open backs have some disadvantages. They will leave the back of the opal vulnerable to damage, especially if the stone is uneven. (If it protrudes slightly from the back, it also won't be very comfortable). Furthermore, the wearer's skin or clothes will influence the colors of transparent to translucent opals in open back settings. Nevertheless, for a particularly valuable opal, buyers will often want an open back. This will demonstrate that the opal is indeed solid, not a doublet or triplet.
Closed settings will affect the color of the opal depending on the color of the backing. On the one hand, opals set in closed silver or white gold settings may look washed out and have a somewhat cooler tone. On the other hand, opals set in closed rose or yellow gold settings may appear warmer in tone, giving already warm-colored opals an even stronger yellow saturation. Yellows aren't typically prized in opals, so consider carefully whether you want a yellow or rose gold closed back setting.
Thin, semi-transparent to translucent precious opals will allow light to shine through and reflect off of the metal backing, creating a strong glare. Since this glare is unrelated to the stone's play of color, it can distract from this characteristic and prized effect. Thus, it's not desirable. Ideally, opals should be set against a black backdrop in a closed-back metal setting. This will enhance both the body color of the stone and the play of color.
Caring for Your Opal Engagement Ring
If cared for properly, opals can last a lifetime, and you can pass them down as heirlooms. However, this will also take a lifetime commitment. Like pearls, opals have special care, cleaning, and storage requirements. Here are some general precautions.
Opal's water content makes it vulnerable to extreme changes in temperature. If exposed to extreme temperatures or dramatic shifts in temperature, opals may crack. Don't store them in sealed plastic bags or safes, which have no moisture in the air, or expose them to heat and dryness for long periods of time. If opals dry out, they may "craze" or develop fractures that appears as a network of angular white lines.
Jewelry should never be exposed to harsh chemicals, and this is especially true for opals. Acids or strong alkaline chemicals will eat away at opal. Therefore, remove your opal jewelry not only before rough activities, like gardening or rock climbing, but also before dishwashing or swimming.
Never put opals in ultrasonic or other mechanical cleaning systems. Warm, soapy water is the safest bet when it comes to cleaning opals. However, don't soak your opal jewelry for extended periods of time. This may damage the glue in doublets or triplets, and some opals may absorb water as well as any contaminants in it.
Style Choices for Your Opal Engagement Ring
Opals have been used in jewelry for thousands of years and can fit into a variety of styles both old and new.
During Georgian, Victorian, and Edwardian times, opals were especially in vogue, prized for their soft, ethereal glow. Jewelers set them in intricate designs.
Opals will look wonderful in engagement ring designs inspired by nature in any style.
A modern designer well-known for her opal jewelry is Paula Crevoshay. She often incorporates vivid pieces of fire and black opal in gold jewelry.
Rare and valuable black opals can help create a unique engagement ring.
Phoebe Shang, GG
A gem lover and writer, Phoebe holds a graduate gemologist degree from the Gemological Institute of America and masters in writing from Columbia University. She got her start in gemology translating and editing Colored Stone and Mineral Highlights for a professor based in Shanghai. Whether in LA, Taipei, or New York, Phoebe spends her time searching for gems to design and being lost in good books.
Never Stop Learning
When you join the IGS community, you get trusted diamond & gemstone information when you need it.
Get Gemology Insights
Get started with the International Gem Society’s free guide to gemstone identification. Join our weekly newsletter & get a free copy of the Gem ID Checklist!