Geologically the Book Cliffs are part of the Mancos formation topped by another layer called the Mesa Verde formation. The Mancos formation was a deep ocean sea bed in the Cretaceous period. Within the Mancos shale layers barite crystals have formed filling gaps between the various shale layers. Years of weathering have exposed some of these shale layers, some of which contain the barite crystals.

Book Cliff barite is considered rare and highly prized due to its water clear color.
Barite is heavy, with a specific gravity of 4.5 due to the barium metal inbedded within the crystal. Barite crystals are somewhat soft with a hardness rating around 3.0 to 3.5, or about the same as copper.

Book Cliff calcite crystals are clear, milky white or slightly brownish color from the surrounding shale. They are much more common than the barite crystals and come from the same area.