The finest slates found in the United Kingdom come from Wales.

1 Panworth. 657.

2 Wray.

3 Hunt's Handbook, Exhibition 1862.

The slates from the Silurian formations of Merionethshire, Montgomeryshire, etc., are generally of a blue or grey colour, and of beautiful cleavage, splitting very thin, and sawn square by machinery. The best-known quarries are those in the Ffestiniog district, such as the Oakeley quarries and those of the Welsh Slate Company.

The slates of the Cambrian formation in Carnarvonshire are of varied colours - blue, purple, green, and dark grey. They are more siliceous than the Lower Silurian slates, and not so easily cleaved. They are therefore thicker and heavier, but they are very hard and ring well when struck. Their edges are not sawn, for the reasons given above. The best-known quarries are those of Penrhyn and Dinorwig.

Many of the quarries produce also slabs of first rate quality.

English Slates are generally thicker and coarser than those from Wales - hard, tough, and very durable. The best known are the green slates from Westmoreland, and the slabs from Delabole in Cornwall.

Scotch Slates are also thick and coarse, and generally contain a large proportion of iron pyrites, which, however, does not interfere with their good weathering qualities.

The best known quarries are those of Ballachulish, Easdale, and Cullipool. They are generally blue.