[1][2][3] It preserves fossils dating back to the early Permian period.

[4][5] The formation is composed most of massive gray fossiliferous limestone with some shale and sandstone, with a thickness in excess of 5,000 feet (1,500 m).

It overlies the Panther Seep Formation[6] with a slight disconformity, and its base is typically a thick biostromal limestone bed.

[8] It intertongues with the Abo Formation in the southern San Andres Mountains.

[5] In the Robledo Mountains, the Hueco is promoted to group rank and divided into (in ascending stratigraphic order) the Shalem Colony, Community Pit, Robledo Mountains, and Apache Dam Formations.