to name but a few. Triassic rocks provided the Radyr stone and also the Quarella stone which was worked at Bridgend. Sutton Stone from South Wales' Jurassic outcrop is a highly regarded limestone freestone that has been used in construction throughout the Vale of Glamorgan, it was also shipped over the Bristol Channel to North Devon and North Cornwall which are both deficient in limestone. The micaceous sandstones of Carmarthenshire's Tilestones Formation were formerly worked to provide roofing material, as were similar flaggy sandstones elsewhere, at least until the burgeoning of the North Wales slate industry in the nineteenth century. Limestone Limestone has been worked on a small scale for burning in limekilns over many centuries. In more recent times it has been quarried for use as aggregate, as a flux for the steel industry and as a feed for the chemical industry. Coal The working of coal in Wales' various coalfields began in earnest with the initiation of the Industrial Revolution. Easily the most significant is the South Wales Coalfield though the contiguous Flintshire and Denbighshire Coalfields were of importance to the economy of northeast Wales. A rather smaller coalfield was worked in Pembrokeshire and a tiny one in Anglesey. Sand and gravel Deposits of glacial and fluvial sands and gravels have been and continue to be worked in numerous areas, principally for the construction industry. Geohazards Wales is not a particularly seismically active country, nevertheless earthquakes of lesser magnitude occur from time to time. Ground stability is more of an issue due both to natural causes and, in former areas of coal and other mineral exploitation, due to mining, surface excavation and spoil deposition. Deep-mining of coal in particular has led to reactivation of pre-existing landslips, notably in the steeply-sided valleys of the South Wales Coalfield. Inappropriate placing of spoil material on such slopes has both overloaded them and disturbed drainage patterns with occasional catastrophic effect as in the Aberfan Disaster of 1966. An extensive programme of stabilisation works across the coalfield followed that event. The contamination of land, groundwater and watercourses is a risk in areas where mineral exploitation has taken place, notably in the Central Wales Orefield and in former coal mining districts. Geological conservation and interpretation Numerous sites have been identified as important earth science localities within the Geological Conservation Review and afforded protection as geological SSSIs. See here for complete list of both biological