William Shakespeare once referred to opal as the “queen of gems.” It’s a fitting label for one of Mother Nature's true wonders. For centuries, opal has enchanted jewelry enthusiasts with its ability to display a prismatic rainbow of colors inside the stone, like an iridescent soap bubble or colorful oil slick. The name “opal” originated from the Greek word opallios, which means “to see a change in color.” Yet not all opals exhibit shifting colors; some have an opaque and matted appearance. Why is this? Keep reading to learn all about the science behind the splendor and discover the many colors of opal along the way.
What Color is Opal?
When people think of opal, they often envision a milky white stone, sometimes with specks of color seemingly “floating” inside. But opal boasts a wide variety of body tones or underlying base colors, including black, gray, brown, blue, pink, purple, green, red, orange and yellow. In stones where play-of-color exists, the colors may be a multi-colored rainbow or have just one or two dominant shades.
What is Opal?
Before digging deeper into how an opal gets its color, it’s important to look at its internal chemical composition. Opal is a hydrated form of silica, a compound of silicon and oxygen frequently found in sand and window glass. Unlike diamonds and most other gemstones, opals are amorphous, meaning they don’t have an organized crystal lattice structure. Instead, they are comprised of microscopic silica spheres (picture tiny balls or marbles), which determine an opal's body color or play of color depending on their size and how they are arranged.
Precious Opal vs. Common Opal
Opals are generally divided into two classes: precious opal and common opal. Precious opal, also known as noble opal, displays play-of-color, a mesmerizing visual phenomenon in which a kaleidoscope of colors appears to flicker and “dance” inside the stone when light hits it at different angles. For this dazzling effect to occur, an opal’s silica spheres must be identical in size and tightly stacked together in a neat three-dimensional grid (like a honeycomb).
When light enters a precious opal, it bends to fit through the gaps between the spheres, then fans out and exits in an array of exquisite colors. Precious opal comes in a wide range of body tones that act as the backdrop for play-of-color, including white, black, gray, blue, red, orange and yellow.
Common opal, also known as potch opal, cannot display play-of-color because its silica spheres are irregular in size and shape and aren’t arranged in an organized structure. Common opals are usually opaque or translucent with a waxy luster. Don’t let the “common” label fool you, however. This opal variety comes in many beautiful pastel colors including pink, blue, green, red, orange, yellow and purple.
How is Opal Formed?
The origin of opal dates to prehistoric times in semi-desert regions like Ethiopia and the Outback in Australia. As seasonal rains drenched the dry Earth, the water percolated through the ground and mixed with silica from sandstone. This thick mineral mix seeped into cracks and fissures in the Earth and slowly solidified (over millions of years) like gelatin in a mold. The hardened silica deposit that remained became opal.
Today, Australia accounts for 95% of the world’s precious opal supply. But opal is also mined in places like Ethiopia, Madagascar, Mexico, Brazil, Peru, and parts of the U.S. (Nevada, Idaho, Utah, Washington, Arkansas and Louisiana).
What Affects Opal Colors?
Three key factors determine the color of an opal:
- The structural arrangement of the silica spheres: If the spheres inside an opal are uniform in size and shape and neatly organized, the opal is precious and will demonstrate play-of-color. If the spheres are random in size, shape and arrangement, they are common or potch opals and will not display play-of-color.
- The size of the silica spheres: Small spheres tend to produce cooler tones such as blue, green, and purple, whereas large spheres reveal warmer tones like red, orange and yellow.
- Trace elements and inclusions: The body tone of an opal can also be impacted by trace elements (copper, iron, etc.) and tiny inclusions (impurities) trapped inside the opal’s silica spheres.
What are the Different Types of Opal?
If you’re looking to add a colorful statement piece to your jewelry collection, opal offers an embarrassment of riches. Here are 11 different opal body colors to consider:
White Opal or Light Opal
White opal is perhaps the most popular and well-known variety in the U.S. and is often associated with the birthstone for October and the 24th wedding anniversary gem. Precious white opal is distinguished by its light gray or pale white body tone, typically showing fluorescent green, blue, pink, red and yellow play-of-color. The blending of colors in a white opal is often so picturesque that it can look as if Claude Monet had a hand in its creation.
In contrast, common white opals are mainly translucent or opaque with a cream-colored or milky-white appearance. Some white opals can display opalescence, an optical effect that occurs when light scatters inside the stone, making it look as if it’s glowing from within. White opals are thought to absorb negative energy and promote compassion, healing, creativity and protection.
Gray Opal or Dark Opal
Gray opal, sometimes referred to as dark opal or semi-black opal, can be precious or common and has a medium gray body tone. It’s less common than white opal but can display stronger play-of-color, like black opal.
Black Opal
Precious black opal is the rarest, most valuable, and most desired opal in the world. Its dark body tone, ranging from dark gray to jet black, provides exceptional contrast for a vibrant play of color. Black opals can produce striking color combinations, including fluorescent green and blue, black and red, orange, red and blue, or an explosion of all these colors at once, resembling something close to a luminous supernova. Precious black opal is almost exclusively mined in the Lightning Ridge region in Australia.
Boulder Opal
If you want the visual appeal of a precious black opal without the outrageous price tag, consider a precious boulder opal. It usually has a dark or light brown base peppered with splashes of vivid neon colors. Unlike other opal forms, boulder opal is still connected to its host rock or the rock it grew inside (usually sandstone, ironstone or basalt). The result is veins of opal in unique colors and patterns woven throughout the stone.
Pink Opal
Pink opal is a common opal that comes in a variety of pink shades, from bright bubblegum to deep rose to light pastel pink. It can be transparent, translucent, or opaque and speckled with streaks or swirls of other colors like salmon, peach, black, white, yellow, and even lavender. The best-known mining locations for pink opal are Peru, Mexico, Australia, and Idaho and Oregon in the U.S. It is said to symbolize love, hope, renewal and healing.
Red Opal
An opal with a red body tone is among the rarest and most valuable types of opal, alongside black. Red opal is sometimes called "fire opal" because it can exhibit the colors of a burning flame, like reddish-orange or reddish-yellow. Most fire opals are translucent or transparent and don't display play-of-color, but the ones that do can show flashes of yellow, orange, green and violet. Red opal is primarily mined in Mexico and Ethiopia and is associated with love, passion, and good fortune.
Blue Opal
Blue opals can be common or precious and come in a range of blue body tones, including bluish-black, royal blue, violet-blue, deep teal, ocean blue, turquoise, and baby or sky blue. Precious blue opals may display fiery flashes of fluorescent green, blue, and purple (picture a satellite image of the Earth's oceans from space). When it comes to common blue opal, the most coveted color is blue-green, or as jewelers describe it, the “color of the Caribbean Sea.” Blue opals generally originate from Peru, Australia, Mexico, Ethiopia, and Oregon and Nevada in the U.S. Blue opal is said to symbolize serenity, balance and self-confidence.
Orange Opal
Orange opal has a predominantly orange body color, sometimes with red and yellow accents. It can be translucent or transparent and may be referred to as a fire opal, like red opal. Precious orange opal is pricey and may display green, yellow, red, blue and purple play-of-color. Orange opals are mined in Mexico, Ethiopia, Australia, Brazil and the U.S.
Yellow Opal
Yellow opal is also in the fire opal family and can exhibit a range of body tones, including pale canary yellow, dark mustard yellow, and bright golden yellow. Precious yellow opal can show green, blue, red, and orange play-of-color. Yellow opals are sourced from Australia, Ethiopia, Brazil and Mexico and are thought to exude a joyful, optimistic and confident energy.
Green Opal
Green opal is a common opal that comes in various shades of green, including deep emerald, mossy green, lime green, yellow-green and muted jade. It is lush and earthy and known for its energy-cleansing and emotional healing properties. Green opal can be found in several regions around the world, including Australia, Peru, Tanzania, Madagascar, Mexico, Brazil and the U.S.
Purple Opal
Purple opals can have a body tone of deep purple, violet, or lavender. Two of the most popular common purple opals are Morado opals from Mexico and Tiffany opals from Utah in the U.S. Morado opals, also known as “Opal Royale,” are purple and white and can sometimes fluoresce or glow under ultraviolet (UV) light. Tiffany opals are predominately purple, white and blue but can feature other hues like pink, yellow and cream. Both varieties feature amazing patterns.
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