Old Moss Lead Vein, also known as Killhope Head, 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 Wear Valley

Wear Valley

Wear Valley was, from 1974 to 2009, a local government district in County Durham, England. Its council was based in Crook.The district covered much of the Weardale area. In the west it was parished and rural, whereas in the east it was more urban...

 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 consists of an exposure of a mineral vein in the valley of the Killhope Burn, just upstream from the North of England Lead Mining Museum

North of England Lead Mining Museum

The North of England Lead Mining Museum, also known as Killhope, is an industrial museum near the village of Cowshill, County Durham, England...

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The vein is visible as a 5-metre thick intrusion

Intrusion

An intrusion is liquid rock that forms under Earth's surface. Magma from under the surface is slowly pushed up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the rock slowly...

 trending northeast-southwest through the Great 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....

. Mineralisation in the vein typifies the inner fluorite zone of the North Pennines

North Pennines

The North Pennines is the northernmost section of the Pennine range of hills which runs north-south through northern England. It lies between Carlisle to the west and Darlington to the east...

 Orefield, with galena

Galena

Galena is the natural mineral form of lead sulfide. It is the most important lead ore mineral.Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms...

 and sphalerite

Sphalerite

Sphalerite is a mineral that is the chief ore of zinc. It consists largely of zinc sulfide in crystalline form but almost always contains variable iron. When iron content is high it is an opaque black variety, marmatite. It is usually found in association with galena, pyrite, and other sulfides...

 in the centre of the vein giving way to fluorite

Fluorite

Fluorite is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon...

 and siderite

Siderite

Siderite is a mineral composed of iron carbonate FeCO3. It takes its name from the Greek word σίδηρος sideros, “iron”. It is a valuable iron mineral, since it is 48% iron and contains no sulfur or phosphorus...

 toward the periphery. The site, under the name Killhope Head, has been designated of national importance in the Geological Conservation Review

Geological Conservation Review

The Geological Conservation Review is produced by the UK's Joint Nature Conservation Committee and is designed to identify those sites of national and international importance needed to show all the key scientific elements of the geological and geomorphological features of Britain...

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