I Piece each. 
Petrified Wood is a fossil. Its formed after the plant materials get buried next to sediment, which protects it from exposure to oxygen and organisms. Once this is done nearby ground water saturated with mineral solids slides through the sediment replacing the original plant material with silicia and other minerals. The plants internal structure changes and its minerals crystalize over a few million years. 
 
This is a great tranformation stone. Its energy aides in the spiritual transformation process. It helps you let go of what no longer serves on the path to ascension.