Valentia Slate from the southwest of Ireland, is herein proposed as a Global Heritage Stone Resource. This Middle Devonian (Givetian) purple to pale green-coloured, fine-grained siltstone comprises the Valentia Slate Formation, part of the Old Red Sandstone which extensively crops out in southern Ireland. The unit, which developed as an alluvial fan, has a thickness of over 3000m and shows a well developed cleavage and low metamorphic grade imposed during the Variscan which produced its slaty fabric. Although quarried from small surface openings from the late eighteenth century, the commercial value of certain horizons of the Valentia Slate Formation was first recognised by the local landowner The Knight of Kerry who commenced its extraction at Dohilla in 1816 for use as roofing slates. The operation was expanded from the 1820s by the Hibernian Mining Company and later by the Valentia Slab Company and its successor, the Valentia Slate Company, which continued to quarry the stone until the late 1870s. Initally stone was extracted from surface workings but since 1840 it has been exclusively obtained from underground workings. From the 1880s the quarry went into decline due to competition from Wales and extraction ceased altogether in 1911 following a large rockfall at the opening to the quarry. It was revived in the 1980s and recent investment has resulted in being able to provide this quality stone to widespread markets. Although not easily split into thin slates Valentia Slate was first used locally for roofing and general building. However, as it could be cut into slabs of a variety of thicknesses and lenghts of up to 3m it was more readily adopted, both nationally and internationally, for use in buildings for window cills, steps, domestic fittings in bathrooms and kitchens, and paving both externally and internally as in the Houses of Parliament in London, the Paris Opera House, and for flagging in a number of British railway termini. The stone was susceptible to and held sharp carving, and it it was also fabricated into headstones, memorials, garden furniture, and shelving. Stone was even exported in the 1870s to Brazil for use as railway sleepers. Craftsmen also fabricated lamps and birdhouses from the material and its most celebrated use was for billiard and snooker tables, a number of which were highly decorative having been enamelled. During the height of production over 500 men were employed quarrying and working Valentia Slate. The first tramway in an Irish quarry was installed in about 1816 and was used to transport stone and sawn slabs from the quarry to Knightstown, some 4km away, where it was further fabricated if required in a dedicated stoneyard prior to exportation from the adjacent slate quay. Today extraction continues and the stone is used for a variety of restoration, decorative and construction purposes. The longevity of its extraction, its versatility of use, and the extent of the exportation of the Valentia Slate makes it worthy to be proposed as a Global Heritage Stone Resource.