Which adjective describes something that is hard and stony, like a rock?

The adjective "petrous" is derived from the Latin word "petrosus," meaning rocky or stony. It is commonly used in contexts that require a description of materials or qualities that are as hard and solid as stone. In geological terms, "petrous" can refer to the denser, harder part of certain structures, such as bones or tissues that have a hard, calcified texture, much like the texture of rock or stone itself.

The use of "petrous" provides an accurate and vivid depiction of something characterized by its hardness, making it the most appropriate choice among the options. The other words have distinct meanings that do not relate to the qualities of being hard or stony.