Opals are among the most mysterious and enchanting gemstones on earth. When we see them polished and shining in jewelry, it’s hard to imagine they came from underground. But what does opal look like in its natural form? This article explores the raw, untouched beauty of opal before it’s refined. You’ll discover how it forms, where it’s found, and what to expect if you ever stumble upon one in the ground.
Understanding Opal: A Natural Marvel
Opal is a mineraloid, not a mineral. That means it doesn’t have a fixed crystal structure. Instead, it’s made of tiny silica spheres arranged in patterns. When light hits these spheres, it bends and reflects, creating opal’s famous rainbow-like play of color.
In its natural state, opal doesn’t always shine with the same fire you see in rings or necklaces. It may be hidden inside rock or covered in clay or sand. But even unpolished, it holds beauty and promise.
The Color of Rough Opal
Opal in the ground can appear:
- Milky white
- Grayish-blue
- Earthy brown
- Bright flashes of color (if the opal is close to the surface)
The play of color may be hidden beneath a dull outer layer called “potch.” This layer is often gray or brown and has no color, but it surrounds or hides the colorful opal beneath.
Where Is Opal Found?
Opals are found in a few places around the world, but Australia is the most famous. In fact, over 90% of the world’s opals come from there. Other countries include Ethiopia, Mexico, Brazil, and the United States.
Australian Opal Fields
Some of the best-known opal mining towns in Australia are:
- Coober Pedy: Known for white opals and underground homes.
- Lightning Ridge: Famous for rare black opals.
- Andamooka: Known for crystal opals.
In these areas, opal forms in sedimentary rock—usually sandstone or claystone—left behind by ancient inland seas. These layers are often dry, cracked, and white or tan in color. Miners dig through these layers hoping to find a flash of color hidden in the rock.
See also: What Is Opal Stone Made Of?
What Does Opal Look Like When It’s First Discovered?
Imagine breaking open a rock and seeing a subtle glimmer—a hint of green, blue, or red. That’s how rough opal first appears. It can be:
- Encased in rock: A thin seam or patch of color running through sandstone or clay.
- Loose nodules: Rounded lumps or pieces, sometimes with visible color.
- Layers: Thin sheets or veins of color in a matrix of dull stone.
The surface may be rough, chalky, or waxy. Some opals show their fire right away. Others need to be cleaned or sliced to reveal their true beauty.
The Role of “Potch” in Identifying Opal
Potch is common opal that doesn’t have play-of-color. It’s often found near precious opal and can act as a signal that opal is nearby. While potch has no gem value, it helps protect and surround valuable material. Skilled miners and cutters learn to “read” potch to find colorful seams.
Types of Potch
- White potch: Pale and dull
- Black potch: Dark and often found near black opal
Opal can grow between layers of potch. The cutter must remove the outer potch carefully to reveal the colorful center without damage.
How Opal Forms in Nature
Opal forms when water rich in silica seeps into the ground. Over time, it settles into cracks, voids, and spaces in rocks. As the water evaporates, it leaves behind silica deposits. This slow process can take millions of years.
Common Natural Settings for Opal
- Old riverbeds
- Volcanic ash layers
- Fossilized wood or bones
In some areas, opal replaces organic material, forming opalized fossils. These are rare and highly valuable. In the field, they may look like chunks of stone with unusual shapes or glints of color.
Different Types of Opal in the Ground
1. White Opal
Often found in Coober Pedy, white opal has a pale body tone with soft flashes of color. It blends easily with the surrounding rock and may be harder to spot unless it’s wet or freshly broken.
2. Black Opal
Found in Lightning Ridge, this rare opal has a dark body tone that makes its colors pop. In the ground, it may look like a dark rock with a glassy surface or sudden flash of green, blue, or red.
3. Boulder Opal
This type forms in ironstone rock. It appears as thin seams or veins of opal running through heavy brown or reddish rock. The opal layer is often small, but very colorful.
4. Fire Opal
Mainly found in Mexico, fire opal has a bright orange or red body color. It often looks like glowing jelly and can be translucent or transparent. In the ground, it may stand out more than other types.
5. Ethiopian Opal
This opal is found in volcanic rock and can be very bright. The ground it’s found in may be dark, and the opal often has a glassy appearance. Ethiopian opals can absorb water, so they sometimes appear cloudy until dried.
What Miners Look For
Experienced miners search for signs such as:
- Color flashes in broken rock
- Opalized wood or shell fossils
- Soft, crumbly white claystone
- Seams running parallel through rock layers
Sometimes, they use black lights or other tools to check for glow or color changes in rock. But often, it’s simple hand tools and sharp eyes that find opal in the ground.
How to Spot Rough Opal Yourself
If you visit a known opal area, keep these tips in mind:
- Look for smooth or waxy surfaces in rocks.
- Check for flashes of color in bright light or sunlight.
- Break open small rocks gently to check inside.
- Wet stones to enhance visibility of color.
Always get permission before exploring private land. In countries like Australia, some fields are privately owned or require special licenses for digging.
What Happens After Discovery?
Once opal is found, it must be cleaned, graded, and cut. This process removes the outer rock and reveals the full color inside. The most skilled cutters study the stone’s patterns to decide how to shape it into a gem.
Stages of Preparation
- Washing and drying
- Inspecting with magnification
- Grinding and shaping
- Polishing
Every piece of opal is unique. Some have bright patches of fire; others have gentle rainbows. This individuality makes each gem special, whether large or small.
The Emotional Beauty of Opal in the Rough
Even before it’s polished, opal has charm. Many collectors and gem lovers keep rough opals because of their natural appearance. Holding a piece of the earth that glows with inner color is a magical experience.
Jewelry designers sometimes use rough or minimally cut opals in organic-style settings. These pieces highlight the natural origins of the stone and celebrate its untouched form.
Conclusion
In the ground, opal may look simple or dull at first. But with a closer look, it reveals a rainbow waiting to shine. From soft seams in rock to glowing nodules in clay, the journey of opal begins far beneath our feet. Discovering opal in the earth is like finding a secret message from nature—beautiful, mysterious, and full of life.
Whether you’re a miner, collector, or jewelry lover, knowing what opal looks like in the ground adds depth to its wonder. Next time you see a polished opal in a ring or necklace, remember the quiet, dusty world it came from—and the beauty hidden in every stone.
Read more:
