Petrified Wood: The Complete Guide

Fact: Silicification can happen in decades to centuries in silica-rich hot springs. The famous deposits are old, but the process can be fast.

Fact: It is mostly silica. Only about 10% of the original organic material may remain.

Fact: That widely quoted figure has been debunked. Repeat photography a century apart shows little loss.

Fact: It likely grew from a 1940s ranger story from Hawai’i. The park has archived more than 1,200 “conscience letters” since 1934.

Fact: Volcanic debris flows moved many of them and set them down upright.

Fact: The park recognizes 14 wood species. The old catch-all name, Araucarioxylon arizonicum, is largely abandoned.

Fact: Commercial wood comes from private land, where owners can legally dig and sell it.

About 208–225 million years, from the Late Triassic.

Iron oxides give reds, oranges, and yellows. Manganese gives blues and purples, and chromium gives green.

Agatized wood is about 6.5–7. Opalized wood is about 5.5–6.

No. Removing anything is illegal, with a minimum fine of $325. Buy from gift shops that sell wood from private land.

Sometimes, but reliable identification needs microscope thin sections of the wood cells.

Arizona (state fossil), Washington (state gem), Louisiana (petrified palmwood, state fossil), and North Dakota (Teredo wood, state fossil).

Yes, though most of it is inexpensive. Rough petrified wood often sells by the pound. Value rises with color, polish, clear grain or growth rings, size, and locality: polished rounds and slabs from Arizona or Madagascar, opalized wood, and pieces with an identifiable tree species are worth considerably more.

Petrified wood itself is common and found on every continent. Brightly colored, solid, well-preserved pieces are much less common, and large logs are protected in places like Petrified Forest National Park in Arizona.

Most petrified wood is millions of years old, but the process does not always take that long. Under ideal conditions, with wood buried quickly in sediment rich in dissolved silica (for example near hot springs or volcanic ash), mineralization can begin within decades to thousands of years. Complete replacement that preserves fine cell detail usually takes much longer.

Trace elements in the silica: iron oxides give red, orange, yellow, and brown; manganese gives black and pink; carbon left from the original wood gives black and gray; and copper, chromium, or cobalt can give rare greens and blues. Pure silica is white or colorless.

Look for wood structure in stone: growth rings on the ends, straight parallel grain along the sides, bark texture, knots, or branch scars. Petrified wood is heavy for its size, hard enough to scratch glass (about 7 on the Mohs scale when silicified), and breaks with sharp, curved edges like quartz. If it has grain but is soft or light, it may be only partly mineralized or simply weathered wood.

Mostly silica, usually as quartz or chalcedony, sometimes opal. Minerals carried by groundwater gradually fill the cells and replace the original wood, copying its structure in stone. Less commonly, wood is petrified by calcite, pyrite, or other minerals.

Famous localities include Arizona (Petrified Forest National Park and nearby private land), Washington (Ginkgo Petrified Forest), Oregon, Utah, Wyoming, Madagascar, Indonesia, Argentina, and Egypt. Glacial deposits can carry it far from its source; our Long Island petrified wood is an example. Shop all petrified wood.