Ty Mawr East slate quarry is located on the south side of the B4418 between Nantlle and Talysarn. This open pit/hillside working opened in about 1860. Water power may have been used for hauling and pumping before steam was introduced. A chain incline and a water balance were were used. Although an external rail connection was absent an internal tramway was in use. Material was removed by cart. In 1882 the quarry employed 20 men but only 150 tons output was recorded in that year. In 1898 32 men were employed. The quarry closed in about 1910.
In 1991 several buildings survived including dressing sheds, engine house and chimney (1890s), alongside the firebox and boiler of a semi-portable steam engine. Also, a haulage incline (possibly water-powered), a wheel pit and nearby chimney for an engine and winder now quarried away (from the 1870s preceding the extant engine house), and bases for a Blondin carriage system. There is also a well-engineered access road.
Sources:
D.Gwyn, Welsh Slate: the Archaeology and History of an Industry (RCAHMW 2015), pp.154-5.
A.J.Richards, A Gazeteer of the Welsh Slate Industry (1991), pp.52-3.

RCAHMW, 16 March 2015