Cassop Vale is a Site of Special Scientific Interest

Site of Special Scientific Interest

A Site of Special Scientific Interest is a conservation designation denoting a protected area in the United Kingdom. SSSIs are the basic building block of site-based nature conservation legislation and most other legal nature/geological conservation designations in Great Britain are based upon...

 in the Durham City district of County Durham

County Durham

County Durham is a ceremonial county and unitary district in north east England. The county town is Durham. The largest settlement in the ceremonial county is the town of Darlington...

, England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

. It lies between the villages of Bowburn

Bowburn

Bowburn is a village in County Durham, England. It is situated about to the south-east of Durham, on the A177, between Coxhoe to the south-east, and High Shincliffe to the north-west.It is part of the Cassop-cum-Quarrington parish.- History :...

 and Cassop

Cassop

Cassop is a village in County Durham, in England. It has a population of about 500 and is located near the city of Durham...

, 7 km south-east of the centre of Durham..

The site is important as one of the larger areas of grassland developed on magnesium limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

. This rock has a restricted distribution in England and grassland associated with it is confined almost entirely to south-east Tyneside

Tyneside

Tyneside is a conurbation in North East England, defined by the Office of National Statistics, which is home to over 80% of the population of Tyne and Wear. It includes the city of Newcastle upon Tyne and the Metropolitan Boroughs of Gateshead, North Tyneside and South Tyneside — all settlements on...

 and County Durham, usually in small, scattered patches that are threatened by quarrying and modern agricultural practices.

Habitats at Cassop Vale include grassland, scrub, woodland and wetland, the last fed by spring-lines. The area also includes recolonised open quarries and mine spoil-heaps, which add to the floral diversity. Several rare and local species are present, including globeflower, Trollius europaeus, birds's-eye primrose, Primula farinosa

Primula farinosa

Primula farinosa, the bird's-eye primrose, is a small perennial plant in the family Primulaceae, native to northern Europe and northern Asia, and farther south at high altitudes in the mountains of southern Europe. This primrose thrives on grazed meadows rich in lime and moisture.-Growth:This...

, lesser club-moss, Selaginella selaginoides

Selaginella selaginoides

Selaginella selaginoides is a non-flowering plant of the spikemoss genus Selaginella with a wide distribution around the Northern Hemisphere. It resembles a moss in appearance but is a vascular plant belonging to the division Lycopodiophyta...

, and moonwort, Botrychium lunaria

Botrychium lunaria

Botrychium lunaria is a species of fern known by the common name common moonwort. It is the most widely distributed moonwort, growing throughout the Northern Hemisphere across Eurasia and from Alaska to Greenland, as well as parts of the Southern Hemisphere including South America and Australia...

. The area also supports a diverse invertebrate fauna that includes populations of the Durham Argus butterfly, Aricia artaxerxes salmacis.