The caves are renowned for their karst qualities, namely the numerous fossils from a long-lived reef complex from the Silurian period.

Fossils include corals, crinoids, brachiopods, gastropods, pentamerids, colonial tryplasmids and trilobites.

Borenore's karst is surrounded by igneous rock that flowed from volcanic eruptions at nearby Mount Canobolas.

Borenore Red marble may be found in The Strand Arcade and in Buckingham Palace.

Examples of the famous Borenore red marble can be seen in Central Station, the Sydney GPO, the Commonwealth Trading Bank Building in Martin Place, and Jenolan Caves House as a mantelpiece.