Petrified wood in our opinion is one of the most interesting and aesthetic materials. The ancient woods was being preserved for millions of years by layers of lava, volcanic ash and sedimentary rocks. Special conditions are required to mineralize a tree which will eventually become a stone while still retaining the pattern of annual tree rings and fibers.
The archaeological layers in which the fossilized trees are found vary depending on geographic location and are on average in the range of 15-240 million of years.
On a hardness scale, a petrified tree is a number 7 out of 10 and positioned in between granite and precious.
It is a very hard material, machinable only with tools with diamond coating.