Source Area: CUMBRIA

Geological Age: ORDOVICIAN

Geological Unit: Borrowdale Volcanic Group (about 450-460 million years old)

Geological Description:

Much of the mountainous central part of the Lake District is formed from the rocks of the Borrowdale Volcanic Group. This complex rock mass was considerably deformed during a period of intense tectonic activity (Acadian Orogeny). A wide variety of metamorphic rock types were formed during this deformation phase and one of the most distinctive products was the green slates. These slates were originally deposited as fine-grained volcaniclastic ash from local volcanic centres in the area. The cleavage planes produced during their subsequent deformation enabled them to be split in thin slabs suitable for roofing or walling stone. More expensive than the ‘industrial’ Welsh slate they were still the principal choice for the roofing of large houses and other prestigious buildings from at least the 18th century onwards.

Source Area: YORKSHIRE

Geological Age: CARBONIFEROUS

Geological Unit: Pennine Coal Measures Group, Elland Flagstone Formation (about 310 million years old)

Geological Description:

Flagstone is so named on account of the thinness of the beds which split easily into flat, parallel sided paving stones or slabs. The fine-grained, thinly bedded, micaceous sandstones known as the Elland or York Flags were deposited as part of a freshwater complex of alluvial streams and river delta systems that formed the vegetated swampland areas of the Coal Measures succession. The concentration of the platy mineral mica into discrete layers within the sandstones enabled the sandstones to be split or riven into thin slabs for roofing, paving or walling stone. In the Elland (Halifax) area of Yorkshire the sandstones were mined (rather than quarried) extensively in the 19th century and supplied, and still supply, paving stone for London and many other industrial towns and cities in England.

Source Area: LINCOLNSHIRE

Geological Age: MIDDLE JURASSIC

Geological Unit: Lincolnshire Limestone Formation (about 165-170 million years old)

Geological Description:

These pale yellow limestones accumulated as shallow marine shell banks and ooid shoals in the tropical seas that, during the Middle Jurassic period, once covered much of central and southern England. The thick beds of limestone that were formed have been quarried extensively since mediaeval times and are probably one of the East Midlands most recognisable building stones. They have been used for decorative carving and walling in thousands of buildings across the region, including Lincoln and Ely cathedrals.

Source Area: NOTTINGHAMSHIRE

Geological Age: PERMIAN

Geological Unit: Cadeby Formation (about 260 million years old)

Geological Description:

The distinctive coarsely crystalline Linby Stone is now the only surviving building stone quarry in Nottinghamshire. Together with its now long closed sister quarries at Bulwell it has supplied stone for hundreds of buildings and construction projects across the city. Quarrying of this thinly bedded, dolomitic or magnesian-rich limestone has continued since at least mediaeval times and it can lay claim to being the only stone that can truly be called Nottingham Stone.

Source Area: SOUTH WALES

Geological Age: CARBONIFEROUS

Geological Unit: South Wales Coal Measures Group (about 305-310 million years old)

Geological Description:

The thick beds of blue-grey Pennant sandstones, because of their hard resistant character, form a plateau of high ground along the valley tops in the South Wales coalfield. The word Pennant, which is probably of Welsh or Celtic origin, means head or top of the valley. The sandstones were deposited as part of a major fluvial channel system that once covered much of South Wales and parts of Gloucestershire. The Pennant sandstone was the principal building stone in both the South Wales and Bristol coalfield areas and is most commonly seen in the thousands of terraced properties that climb the sides of the steep valleys that dissect these coalfield areas.

Source Area: NORTH WALES

Geological Age: SILURIAN

Geological Unit: Nantglyn Flags Formation (about 420-430 million years old)

Geological Description:

This fine grained slate was originally deposited as a thick succession of deep water, thinly bedded, dark coloured, silty mudstones and laminated muddy siltstones. They were deposited in a basin that, during the Silurian (Wenlock), covered much of Mid and North Wales. The basin was gradually infilled by these sediments which were deposited as turbidite flows generated from its shallow margins. Subsequent uplift and deformation during the Caledonian Orogeny transformed these soft basinal deposits into the hard, highly cleaved slate beds that we see today. These slates form part of the extensive Welsh slate belt which has been supplying slate for roofing worldwide since the late 18th century.

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