The Goonbarrow Branch was opened by the Cornwall Minerals Railway in 1893, who operated the line until they were taken over by the
GWR in 1896. The line itself was quite tightly curved and steep in parts with the approach to Carbean being 1 in 39. Originally a locomotive was based in an engine shed at Stenalees to work the branch, and the tight curvature meant that only small engines were used, often in pairs. The last steam locomotives to operate on the branch were
1600 class locomotives, with a pair based at
St Blazey shed for this purpose. Goonbarrow Junction itself underwent several changes to trackwork over the years. The origins were as Wheal Henry siding, with Rosevear siding set back from it, and with a signal box provided at the junction. The original signal box closed in 1893 and was replaced by a new one a short distance south. The sidings remained, and the branch was laid just north with a short loop. Four or five sidings were added parallel to the Newquay branch but accessed via the junction in 1910, and in 1931 further sidings were added, accessed by entering the branch and immediately reversing once the pointwork was cleared. These were known as Rocks siding, Wheal Ann siding, and Hallivet siding. Originally the line was worked as a branch with a staff being collected from the signal box, but from 1964 staff operation was removed and the branch was operated as a long siding. In 2020 satellite images show that the stub of the branch is still acting as a headshunt for the Rocks clay dries that cover the site taken up previously by the three sidings added in 1931, but the rest of the branch is completely lost in the ever expanding clay pits.
Sidings at Goonbarrow In the 1990s Rocks siding and Wheal Henry siding were still in use with Rocks dries still active and two industrial diesel shunters working there, and although these were both stored out of use in 2019, they were both back at work in 2020.
Old Beam siding Requiring reversal to access, the siding was protected by a Ground Frame and served the North Goonbarrow Clay Company. The headshunt was converted into a loop in 1907, and the siding closed in 1969.
Carnsmerry siding and Imperial siding Originally a single siding serving the Imperial Goonbarow China Clay works, a second siding was added to serve the Hensbarrow China Clay Company works at Carnsmerry in 1914, at which point a Ground Frame was installed and the headshunt was converted into a loop.
New Caudledown siding A loop on the north side of the line serving the Lower Lemalson and Caudledown China Clay Company. Branch operation ceased beyond this in 1964 and the "branch" was then operated as a siding.
Rock Hill siding Two short sidings on the north side of the line protected by a Ground Frame. The sidings were removed in 1946.
Old Caudledown siding A single siding protected by a Ground Frame and serving a loading platform.
Cleaves siding A single siding on the west side of the line opposite
Stenalees and protected by a Ground Frame, it was removed in 1933.
Oil siding A short siding on the south side of the line to serve the Carbean China Clay works of J Lovering and Co. The track was laid in late 1925 but was not used until 1926.
New Gunheath siding A short siding on the north side of the line, it was laid in 1921.
Gunheath sidings Two sidings serving the works of H D Pochin and Co. plus a short section of line for reversing towards Carbean, an additional siding was added in 1927. The branch sloped down at 1 in 39 to the sidings, and all points were controlled from a Ground Frame.
Carbean Requiring reversal at Gunheath sidings and then a short run downhill at 1 in 35, there was a loop serving a loading platform and a further reversal here allowed access to the Goods Yard. The points were controlled by a Ground Frame. The siding space at Carbean was quite cramped and shunting often involved multiple movements. By 1992 the location of the siding was partially lost in a clay pit. ==Carbis and Wheal Rose branches==