What Is Petrified Wood?
Petrified wood is an amazing stone. Its look can be quite distinct, featuring the same grain, rings, or other patterns found in wood without being made of organic materials. As a result, it’s a popular item for jewelry.
If you’d like to learn more about petrified wood, including what it is, how it’s made, and more, here’s what you need to know.
What Is Petrified Wood?
Before we dig into what petrified wood is, let’s look at another question that often springs to mind: what does petrified mean? In the simplest terms, petrification is a process where organic matter changes into a stony substance. It’s not unlike ossification in the human body, where cartilage is turned into bone.
For something to be petrified, it needs to have gone through the process of petrification. As a result, petrified wood is simply wood (an organic material) that’s been changed into stone because of that process.
What Is a Petrified Tree?
A petrified tree is just petrified wood. Usually, the only difference in those terms is the size of the piece being discussed. If it’s a large sample that still very much resembles a branch, trunk, or another clearly tree-like segment, it may be referred to as a petrified tree.
However, calling a large, tree-like specimen petrified wood isn’t incorrect. Similarly, referring to a smaller sample as a piece of a petrified tree isn’t wrong, either. It usually a matter of semantics.
How Does Wood Become Petrified?
When it comes to what causes petrified wood, the process is relatively straightforward but rarely occurs. Typically, when a plant dies, it decomposes. For wood to petrify, that decomposition process can’t happen.
To end up with petrified wood, a dead tree or branch needs to be buried in the earth, such as under a layer of mud, silt, or even ash from a volcano. Once covered, oxygen can’t reach the organic matter, preventing or substantially slowing traditional decay.
Water with a high mineral content (or mineral-rich mud) also has to be present near the now-buried tree. As the fluid seeps into the wood’s structure through pores or similar openings, the organic form breaks down slowly. As it does, the physical structure is replaced by minerals, leading to petrified wood.
What Type of Rock Is Petrified Wood?
In most cases, petrified wood contains silica, usually quartz. If you find a piece of agatized wood, it’s simply petrified wood that features agate, a type of chalcedony (which is actually a form of quartz).
With opalized petrified wood, it’s a bit trickier. While opalized wood can refer to petrified wood that’s made of opal, the term also covers any petrified wood that’s ended up with an opalescent sheen.
It’s also important to note that, with opalized petrified wood that actually contains opal, it’s usually common opal. Common opal does have a sheen, but it doesn’t have the characteristic play-of-color you typically find in precious opals (the version most frequently used for jewelry). As a result, opalized wood can actually look a lot like chalcedony petrified wood. In some cases, it even takes scientific testing to tell the difference.
However, there are petrified wood samples featuring precious opal. They are incredibly rare and tend to be more valuable than their counterparts.
Is Petrified Wood a Fossil?
Yes, petrified wood is a fossil. The process essentially preserves the structure of the original specimen while replacing the organic material with minerals.
How Old Is Petrified Wood?
There’s no way to know exactly how old any single piece of petrified wood is because the petrification process is incredibly long. However, some specimens are likely several hundred million years old. Certain samples have been tested using radioisotope dating, giving people a general idea of the age of the piece of petrified wood.
For example, it’s believed that the Petrified Forest in Arizona started to form over 200 million years ago. Radioisotope dating from some samples came back with ages of about 211 million years.
How Long Does It Take for Wood to Petrify?
The process of petrification is lengthy, to say the least. While the exact amount of time isn’t known, the process likely takes millions and millions of years to complete.
What Does Petrified Wood Look Like?
Petrified wood doesn’t have a single look, mainly because the minerals that replace the organic material can vary. Some pieces will resemble real wood, so much so that a person may not realize it’s a petrified piece until they pick it up and feel the weight and texture. However, you also find specimens with incredibly distinct non-wood colors, a lot of clear or white sections, and even opalescence.
Since most petrified wood has a significant amount of quartz, its coloring results from various impurities. The presence of iron or manganese oxide, for example, can tint the quartz, resulting in shades like yellow, red, orange, pink, and beige. Carbon can make it appear black or gray, while copper, cobalt, chromium, manganese, and iron can result in shades of green, blue, or purple.
However, regardless of the color, the piece tends to have wood-like features. For instance, you may see grain or ring patterns.
Is There Petrified Wood Jewelry?
Yes, petrified wood jewelry is available. While it is against the law to remove petrified wood from the Petrified Forest, pieces are found elsewhere. If a specimen comes from private property, it can be used for jewelry, carvings, or any other purpose.
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Petrified wood is a good lapidary stone, particularly the versions featuring quartz. Quartz is durable and relatively simple to work with, shape, or carve. However, opalized petrified wood is more delicate, so jewelry featuring it is less common.
Generally, you won’t find petrified wood jewelry in large chain jewelry stores. However, it can be a popular material with some independent jewelry makers. It’s reasonably easy to find online and in tourist shops in areas where petrified wood is prevalent, such as near the Petrified Forest in Arizona.
When used for jewelry, petrified wood is usually either left in its natural state or turned into cabochons. With those, you can find petrified wood pendants, earrings, and rings with relative ease.
There are also petrified wood beads used to create bracelets, necklace strands, and even pendulums. Additionally, some petrified wood pendants might feature carvings instead of a plain cabochon.