Blue Mountain Quarry is a quarry that made its first appearance in Blue Mountain Mystery. Merrick and Owen are based here. Skarloey, Rheneas, Peter Sam, Sir Handel, Rusty, Luke, Paxton (as well as Thomas, Henry, Spencer and Toby on some occasions), and many other vehicles work here. Blondin Bridge is also located here.
It has replaced the Skarloey Railway Slate Quarry.
Since the seventeenth season, the standard gauge track to the quarry has become dual gauge to accommodate the narrow gauge engines.