The process of petrification begins with three raw ingredients: wood, water and mud. A material formed by the silicification of wood, generally in the form of opal or chalcedony, in such a manner as to preserve the original form and structure of the wood. Also known as agatized wood; opalized wood; petrified wood; woodstone. Petrified wood has been preserved for millions of years by the process of petrification. This process turns the wood into quartz crystal which is very brittle and shatters. Even though petrified wood is fragile, it is also harder than steel.