The front looks like a quartz crystal, the back looks like wood bark. This material can be both petrified wood and rock crystal, this one is half and half. Natural quartz with actinolite, stone comes from Brazil.
It is in its natural, unpolished state. Great for a collectors piece, or could be used in jewelry. Single crystal, sold as pictured.
Approximate size- 47 x 18 x 11 mm, 70 carats