Check the listing for details. Petrified Wood Specimen with Deep Black Core. Listed at 262.00 USD. Wonderful ancient petrified wood slab with a deep black central core, surrounded by subtly banded tones of grey, beige, and naturally formed crystals. Intense black coloration is the result of reduction conditions during fossilization, an environment deprived of oxygen that allowed organic carbon and iron sulfide minerals to be preserved in place of the original woody tissue. Size 16 3/8" L, weight 8 lb. 4.2 oz