On the west side of the Conwy Valley near Llanrwst. Igneous sill intruded into shales producing 2m thick orebody of quartz, calcite and pyrite. The oxidised pyrite has been leached by water filling the workings with sulphuric acid which support copious growths of slimy bacteria.
90,000 tonnes extracted between 1860 and 1875. Reopened by government during WW1, 1,600 tonnes extracted.
Later companies working the deposits were:
| Year | Company |
|---|---|
| 1885 | Trefriw Sulphur Company Ltd. |
| 1888 | Cae Coch Pyrites Ltd. |
| 1889 | North Wales Sulphur Mining Company Ltd. |
| 1895 | Idle |
| 1917 | Ministry of Munitions |
| 1919 | Idle |
| 1940 | Ministry of Supply (Sulphuric Acid Control) |
| post War | Classified as emergency reserve. |
Closed October to April: Roost for Lesser Horseshoe Bats
External Links
Publications (8)
- (1998); BGS - Minerals in Britain - Lead and Zinc; 6 pages
- (2022); CATMHS - Newsletter 146-February; 42 pages
- Bennet & Vernon (1997); Mines of the Gwydyr Forest, Book 7 - Llanrwst: Coed Gwydyr & Cae Coch, Llengelynin: Trecastell & Derwen Deg
- Bennet & Vernon (1997); Mines of the Gwydyr Forest, Book 7 - Llanrwst: Coed Gwydyr & Cae Coch, Llengelynin: Trecastell & Derwen Deg
- BGS - Mine Plans (large, zoomable) - Cae-Coch Sulphur Mine Trefriw; 1 pages
- Ferry, T. (2021); Gwydyr Forests forgotten sulphur industry; 10 pages
- JNCC (2010); Mineralization of England and Wales; pp. 269-273
- Shaw, Donald L. (1971); Gwydyr Forest in Snowdonia - a History (of Forestry); 140 pages
