The Brantwood Musical Stones: where the Rocks and Aggregates came from

Carboniferous Limestones, Shap Beck Quarry Hornfels, Sinen Gill Hanson Aggregates This rock is used in the iRock ‘Blue Granite’, Shap Blue Quarry This rock is used in the main instrument CEMEX UK Materials Ltd. This rock is used in the main instrument Shap Beck Quarry is located just north of the village of Shap, quite close to the granite quarries. The rocks here are however sediments that were deposited in a tropical sea that was the first to flood across the slates and granites of after they formed in the Caledonian Orogeny, around 400 million years ago. They are made of the mineral calcite, which is calcium carbonate and were originally deposited as shells, broken shell fragments and algal secretions in shallow seas. Sinen Gill, looking towards , with slabs of hornfels in the foreground. The limestones from Shap Beck are sent to a A view inside Shap Blue Quarry The hornfels used in these instruments is the Outcrop of hornfels processing plant nearby and used in the large rock that was used in Victorian times to make showing the original layers scale production of lime for steelmaking. Shap Blue Granite is a trade term for this (“beds”), now almost the original lithophones. Recent vertical. The diagonal lines rock, which is neither a granite, nor, to be research has shown that it came from Sinen running through the rock honest, very blue! Strictly, it is another form Gill, north of Keswick, where our material was are a trace of the cleavage of hornfels. It was a volcanic rock originally, that was present when the also collected. The rocks of the northern lakes rocks were slates. formed during the extensive period of volcanic are mainly Skiddaw Slates, deposited originally activity in the Lake District during Ordovician as mud on the sea floor and buried, heated and times, and was originally laid down as an compacted to make slates during the Caledonian ash deposit. Because of its composition, it Orogeny (more information about how this is called an andesite, and is very similar to happens is given under “Green Slates” elsewhere many young volcanic rocks forming around on this board). Subsequently, the slates were the Pacific today. Unlike most of the volcanic intruded by the Skiddaw Granite magma, and rocks of the Lake District, this rock has close to the intrusion the high temperatures undergone subsequent metamorphism due made the minerals react and recrystallise (a to heating by granite, in the same way as the Sinen Gill Hornfels. In this case the intrusion Images of the quarry face demonstrate the pronounced process known as metamorphism) to make jointing (cracks formed as the burden of overlying rocks was a coarse-grained, tough, metamorphic rock responsible for the heating was the Shap Pink eroded away) which makes it possible for this hard rock to known as hornfels. The crystals form a strong, Geological map of The Lake District Granite, a true granite. be quarried efficiently. Based on a map produced by Alan Smith interlocking texture and the rock no longer has a cleavage, but it does weather into slabs reflecting Detail of a weathered surface of hornfels. Long crystals of the mineral andalusite are picked out because they are resistant to the different beds in the original sediment. weathering. Another metamorphic mineral, cordierite, weathers easily and is represented by oval depressions in the surface. Shap Granite, Shap Pink Quarry CEMEX UK Materials Ltd. This rock is used in the iRock The Shap Granite is widely used around Carboniferous Gritstones, Tendley Quarry the UK as a decorative building stone. It is a very coarse grained granite, an igneous Tendley Quarries Ltd. This rock is used in the iRock rock formed by the cooling of a large body In the north of Cumbria an area of thick of molten rock (magma) that was intruded beds of Carboniferous gritstones and coarse into the Cumbrian slates at the end of the grained sandstones was laid down above Caledonian Orogeny, about 400 million the Carboniferous Limestone. This sequence Quarry face in sandstones at Tendley years ago. Large pink crystals of the mineral of rocks also includes black shales – muds Quarry. The slopes above the feldspar are a characteristic feature. Despite sandstone are in soft black shales. rich in the remains of plant material – and being a dense rock, Shap granite is not a a number of coal seams. For many years good musical stone, as you can see if you try The Shap Pink Granite is a very uniform and massive rock; it lacks the coal deposits were mined in the West any compositional layers but is cut by natural fractures (joints) that it out in the iRock. Possibly the large crystals Cumbrian coalfield, centred on Workington, formed as the weight of overlying rock was removed by erosion. contain fine cracks which deaden the sound. while the gritstones and sandstones are still Weathering has exaggerated the quarried at Tendley, near Cockermouth. orange layering in this sandstone.

Red Sandstone, St. Bee’s Head This rock is used in the iRock

A series of red sandstones are found around the outer edge of Cumbria and are best known from the Vale of Eden, near Penrith, and the coast south from St. Bee’s Head. They are mostly desert sandstones of Permian and Triassic age, formed from wind-blown sand dunes and river deposits. Many of these rocks are fairly soft but some are harder and are used for building stones. They are quite porous, which means that some of the rock layers are a good source of groundwater, but it also explains why they do not make good ringing rocks.

Elterwater Quarry Burlington Slate Quarries This rock is used in the iRock

Guide to the Rocks

Green Slates, High Quarry Geological Period Rock type High Fell Greenslate Co. Ltd. This rock is used in the main instrument

Because they are now all lined up in the same direction, this means the rock splits into slabs Desert Red Sandstones parallel to the aligned grains. This structure is Permian -Triassic some shale layers and termed cleavage and means that it is easy to (280-195 million years) evaporite deposits. In general do not ring. extract thin slabs of rock, such as might be

Slabs of grey-green slate awaiting processing used for shelves, cills, tiles or work tops.

The green slates used in the musical instrument are from High Fell Quarry located to the north of Coniston. Gritstones with some The green slates are part of the Borrowdale A view inside Carboniferous shale beds and local coal High Fell Quarry (345-280 million years) measures. Generally do Volcanic Group and were deposited originally not ring. as volcanic ash in shallow waters. They often contain fine layering produced as the ash settled in the water but they can also include larger fragments of volcanic rock. They were compressed to produce the typical Green Limestones, often rich in Greywacke, Holmescales Quarry fossils. Include hard bands Lake District Slates during the Caledonian Detail of the quarry Carboniferous that provide ringing rocks. surface showing Bardon Aggregates This rock is used in the iRock (345-280 million years) Orogeny, around 400 million years ago. These rocks are used in natural joints that both instruments. When the rocks were squeezed, the platy also serve to break up the rock, this mineral grains in the rock re-grew at right time across the angles to the direction of the pressure. cleavage direction.

Windermere Group sandstones and slates, Loading at the quarry face. Silurian with Coniston Limestone (435-395 million years) Graywackes are a type of sandstone in at the base. Include a few Low Brandy Crag Quarry which grains of different sizes are mixed ringing varieties. Burlington Slate Quarries This rock is used in the iRock together, and range from mineral sand to rock fragments to clay. They are usually in bands separated by slaty layers, and are crushed for

aggregate. As the name suggests they are An example of what quarry workers call a ‘peze’; a large isolated block Borrowdale Volcanic dark grey in colour. of greywacke that would have originally been in a matrix of slate. Group: lavas, ash deposits and lake sediments of Broughton Moor Quarry Ordovician volcanic materials, now (500-435 million years) metamorphosed to slates. Burlington Slate Quarries This rock is used in the iRock Include a number of ringing varieties used in Carboniferous Limestones, Stainton Quarry both instruments. TARMAC Ltd. This rock is used in the main instrument Skiddaw Group slates. Tuff, Ghyll Scaur Quarry Generally do not ring Aggregate Industries This rock is used in the iRock Cambrian-Ordovician except where Tuff is a volcanic rock, originally deposited (~530-485 million years) metamorphosed to as fine grained volcanic ash and rock hornfels close to granite fragments and subsequently compacted and intrusions. compressed during the Caledonian Orogeny. The tuffs from Ghyll Scaur have what is called a high polished stone value (PSV) which The extent of the quarry becomes clear when Quarry face in a thick bed of hard limestone. seen from the air. means they are very resistant to wear. This Image courtesy of TARMAC Ltd.

Quarry face in typical green tuff, part of the Borrowdale Volcanic makes them an excellent material to be used Grop. Image courtesy of Eric Johnson as non-slip surfaces on motorways and roads. At least two layers of ringing rocks are Igneous Intrusions. Mainly present in the Carboniferous Limestone granite, including the Shap Blocks of limestone Ordovician & Devonian and Skiddaw granites. worked at Stainton Quarry, which is located awaiting processing. Generally do not ring near the village of Stainton with Adgardley, The reddish brown south Cumbria. surfaces have been Kirkby Moor Quarry stained naturally by Limestones are sedimentary rocks, and iron-oxide in soil that Burlington Slate Quarries This rock is used in the iRock has washed down these were deposited in a warm, tropical into cracks in the sea that covered northern about limestone. 350 million years ago. They are made of the mineral calcite, which is calcium carbonate Sandside Quarry and were originally deposited as shells, Detail of a Stainton limestone TARMAC Ltd. This rock is used in the iRock broken shell fragments and algal secretions in seen under the shallow seas. After the sediment was buried, microscope. At the calcium carbonate recrystallised and the centre is the infilled the original pore spaces between the fossil shell of a tiny marine organism, particles, making a hard, compact rock with little more than surprising acoustical properties. 1mm across.

Funded by: Ruskin Rocks Team and School of Earth and Environment, University of Leeds A collaborative project led by the University of Leeds

Further information at www.ruskinrocks.org.uk