Fossil Wood Also known as 'petrified wood'

Most fallen trees rot away completely, leaving no trace of their presence BUT petrification of the trunk could occur when the tree fell over in old age (or was wind blown or washed down into a river bed during seasonal floods – or was even pushed over by a dinosaur!). If the trunk became completely covered in sediment, excluding oxygen and was in an area where mineral rich water was flowing through the sediment, mineralization would gradually have taken place. Deposits of minerals (usually silicon dioxide / agate) would replace the organic lignin and cellulose in the plant cells, forming solid fossil wood. Some petrified wood is formed in areas smothered in volcanic ash, e.g., the Petrified Forest on the island of Lesbos, Greece.

If minerals are dissolved in the water flowing around the trunks, their characteristic colours may appear in the fossilwood.

For example:

Silica: Grey, white

Manganese oxides: Black

Manganese: Pink, orange

Iron oxides: Red, yellow, brown

Copper, chromium, cobalt: Green, blue

Surprisingly, fossilwood makes extremely attractive spheres and some other worked products. Fossilwood sometimes occupies the borderlands between rocks and crystals, especially when slices include exquisite areas of individual crystals.

Some fossil wood specimens show areas of preserved annual growth rings in horizontal cross-sections of the trunk. These recorded the growth of the tree, each ring representing the annual increase in the tree’s girth. Trees that grew in areas of the world with big seasonal differences between winter and summer show these more clearly than those growing in tropical regions where growth can take place all year. Often details of the bark are beautifully preserved.

Many Conifers (and broadleaved species which evolved later) have been found in various sites around the world and have given valuable evidence of climates of the past – for example, much of the fossilwood found in Arizona is from the Araucariaceae family (the 'monkey puzzle' family). This family is now extinct in the wild in the northern hemisphere but flourished there when the climate was considerably warmer and wetter than experienced today.

The oldest specimens found are thought to date back 250–200 million years ago to late-Triassic times. Far younger samples have also been discovered, such as the Lesbos find which is thought to be only 20–15 million years old.

Probably the largest specimens have come from the Santa Cruz area of southern Argentina with trunks measuring up to 30m (100’) long and 3m (10’) in diameter. That petrified forest has been, understandably, classified as a National Monument! The Petrified Forest of Lesbos covers an area of over 150 square kilometres and even includes large upright trunks with root systems still in place.

Fossil wood is graded as 7 on the Mohs scale (the same as quartz due to its silica content).

Crystals (UK) has been obtaining its supplies of very varied and fascinating specimens from Madagascar for many years. We aim to stock both large slices with particularly fine colouring and detail as well as smaller pieces showing lovely bark textures.

For many years, Crystals (UK) sourced fossilwood from Australia. The prospector and land-owner benefitted equally and it was practice to fill in a trunk being worked on below the surface to prevent other prospectors finding it.