Petrified wood is the remains of trees that grew in the Permian period, about 250–285 million years ago, and in the Carboniferous period, approximately 299–360 million years ago.

The scientific name for fossilized wood is “petrified, ” derived from the Greek word “petro” — “stone.” The process of petrification took place underground, when trees were completely buried by sediment, but did not decay due to lack of oxygen. For instance, many trees were preserved after being covered by layers of ash from volcanic eruptions.

Water, rich in minerals, flowed through the sediment and brought minerals into the plant cells. These were often silicates, such as quartz. Lignin and cellulose, polymers found in wood, decomposed. As a result, what remained was stone that retained the original microscopic structure and shape of the tree. In some cases, even growth rings could be discerned.

Thus, petrified wood is no longer a plant, but stone. There are no organic compounds in it. Wood served not only as a mold for the stone but also provided a bit of carbon, which gave the petrified wood its rich color.

The brightest shades were achieved when metals entered the tree cells. The range of colors is quite wide: carbon gave a black color; cobalt provided green or blue; iron oxide resulted in red, brown, or yellow; manganese produced pink or orange; and manganese oxide created black or yellow.

Petrified trees could either be coniferous or deciduous. In Russia, deposits of fossilized wood have been discovered in Central Siberia, Primorye, Kamchatka, and Chukotka.

Petrified trees have been used as raw materials for jewelry production since ancient times. The value of the samples is linked to their unique shapes, patterns, and their age of millions of years.

Petrified trees were also used in folk medicine. For example, the Mongols applied slices of petrified wood to their joints to treat arthritis.

Amulets in the form of figurines of gods, helper spirits and animals were made from petrified wood. These amulets were believed to protect houses from fires, floods, and other natural disasters.