Petrified Wood Identification: How to Identify Petrified Wood

You're walking through a desert, you see what looks like a chunk of wood lying on the ground, and you pick it up. Except it's heavy. Like, really heavy. And hard. And it doesn't feel like wood at all. It feels like rock.

Congratulations, you might've just found petrified wood.

Petrified wood is one of the coolest fossils out there because it looks like wood but it's actually stone. The organic material has been completely replaced by minerals over millions of years, preserving every detail of the original tree. Bark, rings, grain, knots—all frozen in stone.

This guide will teach you how petrification works, how to identify petrified wood, where to find it, and what you need to know about collecting it legally.

What Is Petrified Wood?

Petrified wood is fossilized wood where the organic material has been replaced by minerals, most commonly silica (quartz). The process is called permineralization.

Here's how it happens:

A tree dies and gets buried quickly, usually by volcanic ash, sediment, or a flood. The lack of oxygen prevents normal decay. Over time, mineral-rich groundwater seeps into the wood. Silica (or other minerals like calcite, pyrite, or opal) gradually replaces the wood's cellular structure, atom by atom.

What you end up with is a rock that looks exactly like wood. The original shape, texture, and internal structure are preserved in stunning detail. Even the growth rings and bark are visible.

This process takes millions of years. Most petrified wood you find is 50 to 200 million years old, though some specimens are older.

How to Identify Petrified Wood

Petrified wood is surprisingly easy to identify once you know what to check. Here are the key tests:

1. Weight

Petrified wood is much heavier than regular wood. If you pick up what looks like a log and it feels like a boulder, it's petrified. Silica is dense (specific gravity ~2.6), so even small pieces feel substantial.

2. Hardness

Petrified wood has a hardness of about 7 on the Mohs scale (if it's silicified). That means it scratches glass easily. Regular wood is soft; you can dent it with your fingernail. Petrified wood? Not a chance.

Try the scratch test: take a sharp edge and try to scratch a glass bottle. If it leaves a clear scratch, it's likely petrified wood or another hard mineral. If it doesn't, it might be calcified wood (softer, replaced by calcite instead of quartz).

3. Wood Grain and Tree Rings

The giveaway: visible wood grain, tree rings, or bark texture. Petrified wood preserves the cellular structure of the original tree. You can often see:

• Growth rings (concentric circles)
• Wood grain patterns
• Knots and burls
• Bark texture on the outside
• Sometimes even insect borings or fungal decay

If it looks like wood and feels like rock, it's probably petrified wood.

4. Color

Petrified wood comes in a wild range of colors, depending on which minerals replaced the original wood:

• Brown, tan, or beige: Pure silica (quartz)
• Red, orange, or pink: Iron oxide (hematite)
• Yellow or gold: Limonite or sulfur compounds
• Green: Copper minerals
• Blue or purple: Manganese oxide
• Black: Carbon or pyrite
• White or gray: Pure quartz or opal

Some pieces have multiple colors in wild, swirling patterns. These are highly prized by collectors.

5. It Doesn't Burn

This is the ultimate test (though don't do this if you care about preserving the specimen). Petrified wood will not burn. It's rock. Regular wood, even ancient wood, will burn if you light it. If your "wood" is fire-resistant, it's petrified.

6. Smooth, Glassy Fracture

When petrified wood breaks, it shows a conchoidal fracture: smooth, curved, shell-like surfaces. This is characteristic of quartz. Regular wood splinters. Petrified wood breaks like glass.

Where to Find Petrified Wood

Petrified wood forms in areas with ancient forests that were buried by volcanic eruptions, floods, or sediment. Look for regions with:

• Volcanic activity (past or present)
• Sedimentary rock layers (sandstone, shale, mudstone)
• Desert badlands or eroded areas where layers are exposed

Best Locations in the United States:

Arizona: Petrified Forest National Park

The most famous petrified wood site in the world. Millions of logs from the Triassic period (225 million years ago) are scattered across the desert. The wood is brilliantly colored: reds, yellows, purples, and blues.

Important: Collecting is illegal in the National Park. You can look, photograph, and admire, but don't take anything. People have been prosecuted for pocketing even small pieces.

Washington: Ginkgo Petrified Forest State Park

Eastern Washington has massive deposits of petrified wood from ancient forests buried by lava flows. The Ginkgo forest contains over 50 species of petrified trees, including ginkgo, which is rare.

Collecting is allowed in some areas outside the park. Check BLM land regulations.

Wyoming: Yellowstone and Surrounding Areas

Petrified forests exist in Yellowstone National Park and nearby areas. Some layers contain upright petrified trees still in their original growth positions.

Again, collecting in National Parks is illegal. But surrounding BLM and private land may allow it.

Texas: Big Bend and Surrounding Areas

Petrified wood is scattered throughout west Texas. Collectors find colorful specimens in deserts and along creek beds.

Louisiana: Petrified Palmwood

Louisiana has petrified palm wood, which shows distinctive rod-like structures. It's found in gravel pits and river deposits.

North Dakota and South Dakota

The Dakotas have extensive petrified wood deposits from the Paleocene epoch. The wood is often found in badlands and eroded areas.

Other Notable Locations:

• Oregon, Nevada, Utah, Colorado (western deserts and volcanic regions)
• Argentina (Patagonia has massive petrified forests)
• Madagascar, Australia, Egypt (Sahara Desert)

Legal Considerations: Can You Collect Petrified Wood?

This is important. The rules vary by location:

National Parks: NO

Collecting rocks, fossils, or petrified wood is illegal in all U.S. National Parks. This includes Petrified Forest, Yellowstone, Badlands, and others. Penalties include fines ($100-$5,000) and potential jail time for large-scale theft.

State Parks: Usually NO

Most state parks prohibit collecting. Check specific park regulations.

BLM Land and National Forests: SOMETIMES YES

The Bureau of Land Management and U.S. Forest Service generally allow casual collecting for personal use (not commercial sale). Limits are usually around 25 pounds per person per day, or a reasonable amount that fits in a backpack.

However, some areas are off-limits. Check with the local BLM or Forest Service office.

Private Land: YES, with Permission

If you have the landowner's permission, you can collect freely. Some ranchers and landowners allow rockhounding for a fee or as a courtesy.

Commercial Collecting Requires Permits

If you're collecting to sell, you need a permit on most public lands. This includes petrified wood sold at rock shops and online.

Petrified Wood vs. Other Fossils

Petrified Wood vs. Fossilized Bone

Both can look similar, especially if they're broken or weathered. Key difference: petrified wood shows wood grain and tree rings. Fossilized bone has a porous, honeycomb-like internal structure (trabecular bone). Bone is also slightly lighter.

Petrified Wood vs. Agate or Jasper

Agate and jasper are also silica-based and can be colorful. But they don't have wood grain. If you see tree rings or bark texture, it's petrified wood. If it's smooth with banding or patterns but no organic structure, it's probably agate or jasper.

Petrified Wood vs. Regular Old Wood

Ancient wood (driftwood, bog wood, subfossil wood) can be thousands of years old and look petrified, but it's still organic. It's lighter, softer, and will burn. Petrified wood is mineralized and stone-hard.

What to Do If You Find Petrified Wood

1. Document It

Take photos of the specimen in place. Note the location, surrounding geology, and any other petrified wood nearby.

2. Check If Collecting Is Legal

Are you in a National Park? State park? BLM land? Private property? Know the rules before you take anything.

3. Collect Carefully

If collecting is allowed, take only what you can carry and use. Don't disturb the area unnecessarily. Leave some for others to find.

4. Clean and Display It

Petrified wood can be cleaned with water and a brush. For extra shine, you can polish it with rock tumblers or by hand. Cut and polished petrified wood makes beautiful display pieces, bookends, and countertops.

5. Learn More

Join a local rockhounding club or paleontology group. Experts can help you identify the species of tree, estimate the age, and appreciate the geological history.

Why Petrified Wood Is Amazing

When you hold petrified wood, you're holding a snapshot of an ancient world. That tree grew 100 million years ago, in a climate utterly different from today. It might have been a tropical rainforest in what's now Arizona. Dinosaurs could have walked past it.

Then a volcanic eruption or flood buried it, and over eons, minerals seeped in and turned it to stone. Every cell, every ring, every knot preserved in perfect detail. It's geology, biology, and art all in one.

Not Sure If It's Petrified?

If you've found something that looks like wood but feels like rock and you want a fast ID, try Rock Identifier. Snap a photo and the AI will analyze whether it's petrified wood, fossilized bone, or something else entirely.

And if you want to learn more about identifying rocks and fossils in the field, check out our beginner's guide to rock identification or explore the 15 most common backyard rocks you might encounter.