What is Dendritic Opal?
Dendritic opal is a type of common opal that’s visually striking, thanks to its dendritic (or tree-like) inclusions. These aren’t fossils, but rather metallic oxides, often manganese and iron.
The unique patterns form as silica-rich solutions deposit silica in sedimentary rocks, with manganese or iron compounds creating the branching shapes we see. This type of opal is prized for its beauty, potential metaphysical properties, and collectibility.
This article will dive into the formation of dendritic opal, its unique properties, the variations you might find, its history, the meanings people associate with it, its uses, and where you can find it.
Formation and geological background
Dendritic opal is a fascinating stone, but how does it come to be?
The formation process
Dendritic opal usually forms in sedimentary rocks where silica-rich solutions are present. These solutions seep into the cracks and crevices of the “host” rock.
Over time, manganese and iron oxides form the stone’s signature dendritic patterns. The word “dendrite” comes from the Ancient Greek word for “tree-like,” which makes sense when you see the stone’s branching inclusions.
It’s worth noting that, despite the plant-like appearance of these inclusions, they aren’t actually fossilized plants.
Geological settings
Dendritic opal is commonly found in sedimentary rocks, where the host rock provides a sort of matrix for the opal to form within.
Technically, dendritic opal is classified as a mineraloid, not a mineral. One of the things that distinguishes it from a mineral is its water content, which can be as high as 30%.
What are dendritic opal’s physical properties?
Dendritic opal is a relatively hard stone, rating 5.5 to 6.5 on the Mohs hardness scale. Its density ranges from 1.9 to 2.3 grams per cubic centimeter, giving it a specific gravity in the same range: 1.9 to 2.3.
In terms of appearance, dendritic opal is typically translucent to opaque. Many stones have a milky, opalescent sheen. The colors are highly variable and can include white, yellowish-brown, black, brown, green, gray, blue, red, purple, and yellow.
When polished, dendritic opal has a vitreous (glass-like) or waxy luster. It has a refractive index (RI) of 1.44 to 1.46.
Dendritic Opal Varieties
Dendritic opal comes in a wide range of colors and patterns. The base color of the stone can vary from white and cream to yellow-brown, gray, and even shades of green, blue, and red. This base color significantly impacts how the overall stone looks.
The patterns formed by the inclusions can also vary quite a bit, ranging from delicate, fern-like shapes to bolder, more branching formations. Some dendritic opal is even called “landscape opal” because the patterns look like tiny scenic landscapes inside the stone.
You might also hear dendritic opal referred to as “moss opal” or “mossy opal,” highlighting the moss-like appearance of the inclusions.
Where Does Dendritic Opal Come From?
Dendritic opal can be found all over the world. Some of the largest deposits are in Australia, the United States, Mexico, and Madagascar.
Here’s a list of specific places where you might find dendritic opal:
- Australia (especially Queensland)
- United States (Nevada, Idaho, Oregon)
- Peru
- Mexico
- Madagascar
- Turkey
Compared to precious opals, dendritic opal is pretty easy to find. This is one reason it’s a popular choice for jewelry and ornamental objects.
Dendritic opal vs. dendritic agate and merlinite
Dendritic opal is often confused with other stones that have similar inclusions, so here’s a quick guide to help you tell them apart.
Dendritic opal vs. dendritic agate
Dendritic opal and dendritic agate share a similar look, but they’re very different at the elemental level.
- Mineral classification: Dendritic opal is a mineraloid, while dendritic agate is a mineral. This is a key distinction in their geological classification.
- Hardness: Dendritic agate is a 7 on the Mohs hardness scale, while dendritic opal is a 5.5 to 6.
- Structure: Agate is a type of chalcedony, a microcrystalline quartz. Opal, on the other hand, is an amorphous hydrated silica.
Dendritic opal vs. merlinite
Merlinite is yet another stone that can be confused with dendritic opal.
- Composition: Merlinite is a combination of quartz and psilomelane, which is a barium manganese oxide. While merlinite can have dendritic inclusions, its mineral composition is different from that of dendritic opal.
- Appearance: Merlinite typically has black dendrites in a white or light matrix, creating a distinct contrast.
History, Meaning, and Symbolism
Dendritic opal has a rich history and is associated with a number of symbolic meanings.
Historical Significance
In ancient times, dendritic opal was considered a stone of magic and power. People believed it held special properties that could influence events and provide protection.
Symbolism
Dendritic opal is often linked to balance, grounding, and a strong connection to the Earth. It’s also thought to enhance intuition, self-awareness, and connection with the natural world. Some associate it with the sun and the zodiac sign Leo, symbolizing vitality and creative energy.
Metaphysical Properties
Proponents of crystal healing believe dendritic opal can support the circulatory and immune systems. It’s also thought to alleviate dizziness, inflammation, and kidney problems. Please note that these claims are based on anecdotal evidence and should not replace professional medical advice.
What are dendritic opals used for?
Dendritic opals are beautiful stones that people use in a number of ways:
- Jewelry: You’ll often find dendritic opals in pendants, rings, and earrings. Jewelers tend to cut them into smooth, rounded “cabochon” shapes to really show off the tree-like patterns inside.
- Lapidary Arts: Because of their unique look, dendritic opals are also used for carvings and other decorative stone work.
- Collector’s Items: Mineral collectors love dendritic opal specimens because no two are exactly alike.
- Metaphysical Practices: Some people believe dendritic opals can help with spiritual growth and understanding. Because some associate them with the crown chakra, they use them to promote clarity and connection to the universe.
Frequently Asked Questions
Is a dendritic opal a real opal?
That’s a great question! Yes, a dendritic opal is a real opal, but it’s a bit of a special case. Unlike precious opals that flash with vibrant colors, dendritic opals are known for their beautiful tree-like inclusions, called dendrites. These inclusions are usually made of iron, manganese oxides, or other metallic minerals that seep into the stone over eons.
What is the rarest form of opal?
When we talk about rare opals, Black Opal is often at the top of the list. Found predominantly in Lightning Ridge, New South Wales, Australia, Black Opal is highly prized for its dark body tone, which allows the vibrant play-of-color to really pop. But it’s not just the color; the intensity and pattern also play a huge role in determining its rarity and value. Harlequin patterns, for example, are among the most coveted.
That said, it’s really hard to say definitively what the absolute rarest opal is, because rarity can be subjective and depend on a whole bunch of factors beyond just the type of opal. For example, a particularly stunning and large example of a common opal type with an unusual play of color could be considered rarer than a smaller, less impressive black opal.
Conclusion
Dendritic opal is a gorgeous and unusual gemstone. What sets it apart is the presence of dendrites, branching tree- or fern-like inclusions that make each stone unique. From its formation to its physical properties and even its metaphysical associations, dendritic opal has a lot to offer gem and mineral collectors.
Whether you choose to wear dendritic opal as jewelry, collect it as a specimen, or connect with its potential healing properties, this gemstone provides a tangible connection to the natural world. Keep in mind that opal is a relatively soft stone, so it’s best to handle it with care to prevent scratches and maintain its beauty for years to come.