Oil shale is best described as which of the following?

• A. Oil shale is a fine-grained sedimentary rock.
• B. Oil shale is a metamorphic rock formed by intense heat.
• C. Oil shale is a liquid crude oil deposit.
• D. Oil shale is an igneous rock with tar pockets.

Answer: (A)

Understanding sedimentary rocks is key here. Oil shale is a fine-grained sedimentary rock because it forms from the gradual deposition and compression of tiny particles like clay and silt, creating a layered rock. It contains kerogen, an organic material that can yield oil when heated, but it isn’t actual liquid crude oil in place. That’s why it’s not a liquid oil deposit. It also isn’t metamorphic, which would involve transformation of existing rock under high heat and pressure, nor is it igneous, which forms from molten rock. So describing it as a fine-grained sedimentary rock best fits its origin and composition.