# Purbeck Marble - Page: https://taslar.bumba.tr/en/stones/purbeck-marble/ - Turkish: Purbeck mermeri - Also known as: Purbeck marble - Kind: Rock - Classification: Rocks › Sedimentary rocks › Chemical and biochemical - Hardness (Mohs): 3 - Specific gravity: 2.7–2.8 g/cm³ - Colours: bluish grey, grey, green, red, brown - Composition: Fossil-rich limestone: densely packed shells of the freshwater snail Viviparus set in a fine lime-mud matrix and bound by crystalline calcite cement. Glauconite (an iron-rich green mineral) gives the green colour; iron oxides such as hematite or limonite give red and brown shades. - Texture: Speckled, with cross-sections of snail shells, mostly smaller than 8 × 4 mm, set in the matrix. Scientifically a biomicrudite (large fossil fragments in fine mud). Its beds are never more than 1.2 m thick and are often much thinner. - Value ladder: 4/9 step, Fine dimension stone and ore A “marble” built of snail shells: the Dorset stone that gave England's medieval cathedrals their slender dark columns. Purbeck Marble is a limestone packed with the shells of freshwater snails, quarried on the Isle of Purbeck in Dorset, southern England. It is called “marble” because it takes a fine polish, but it is not a true marble transformed by heat and pressure. It has been used since Roman times, and won its fame in the 12th and 13th centuries in the slender shafts, tomb effigies and fonts of great churches such as Salisbury, Canterbury and Westminster. ## How does it form? Purbeck Marble was laid down about 143–137 million years ago, at the start of the Early Cretaceous (in the Berriasian stage). At that time the area of today's Dorset held waters teeming with freshwater snails called **Viviparus**. The shells of dead snails sank with fine lime mud and built up into dense shell beds. Over time the mud hardened, the spaces between the shells filled with crystalline **calcite** cement, and the stone became compact enough to take a polish. These beds lie towards the top of the Durlston Formation in the rock sequence geologists call the **Purbeck Group**, and none is more than 1.2 metres thick. Iron oxides (hematite, limonite) in some beds give the stone red or brown colours, while **glauconite** in others makes it green, or occasionally blue. Because the stone never went through metamorphism, the snail shells are still clearly visible. ## What is it used for? - **Roman times:** In Roman Britain the stone was used for inscriptions, architectural mouldings, veneers, and mortars and pestles. - **Medieval cathedrals:** It was used most between 1170 and 1540, above all in the 13th century for tall, slender, clustered shafts. It can be seen as columns, panels and flooring in virtually all the cathedrals of southern England, among them Salisbury, Canterbury, Exeter, Ely, Norwich, Chichester, Lincoln, Southwark, Llandaff and Westminster Abbey. The arches of the Temple Church in London also rest on Purbeck Marble shafts. - **Tomb effigies and fonts:** From the mid-13th century, makers of tombs and effigies specialised in this stone; at Canterbury it was used for the tomb of the Black Prince and those of several archbishops. Many village churches have fonts made of it. - **Later times:** Its use declined in the 14th and 15th centuries. Kingston church (1874–1880) is a remarkable Victorian example, and the sculptor Emily Young works with the stone today. The stone's weak point is damp: the small amount of iron in its cement rusts in wet conditions and the snail shells fall apart. That is why it lasts best indoors. ## Where is it found? The Purbeck Marble beds run right across the **Isle of Purbeck** in south-east Dorset, from **Worbarrow Tout** in the west to **Peveril Point** at Swanage in the east. Pits dating from Roman times, counted among England's earliest stone quarries, stretch along the valley side north of **Langton Matravers**; in the Middle Ages they were extended westwards for the cathedrals. The village of **Corfe Castle** was the centre of medieval marble carving, and the stone was quarried close to the coast and shipped to distant towns. Other limestone beds of Purbeck are still quarried today. ## How to recognise it - On a polished surface, pale ring- and crescent-shaped cross-sections of small snail shells are packed closely in a dark matrix. - It is usually bluish grey or greenish; reddish and brown kinds also occur. - Pieces left outdoors or in damp places for a long time roughen, the snail shells begin to fall apart and rust stains may appear. - Being a limestone, it fizzes in dilute acid and can be scratched by a steel knife. ## Fakes and imitations - Sussex Marble, from south-east England, is also a limestone full of Viviparus snail shells and is confused with Purbeck Marble. The shells in Sussex Marble are larger; those in Purbeck Marble are usually smaller than 8 × 4 mm. - Not every limestone from the Isle of Purbeck is Purbeck Marble: the name is given only to beds containing a large proportion of Viviparus shells. ## What determines its value? As a building and ornamental stone, its value depends on the thickness and soundness of the bed, the evenness of the colour (blue, green or red), a dense and even spread of snail shells and how well it polishes. Because it decays in damp conditions, sound, crack-free pieces for indoor use are the most sought after. Its real value comes from its place in medieval cathedrals and the need for the same stone when those buildings are repaired. This information is educational, not buying, selling or investment advice. Value varies enormously with quality and treatment. ## Myths and misconceptions - Myth: Purbeck Marble is a true marble. Fact: It is called marble because it takes a fine polish, but it is not a rock transformed by heat and pressure. It is a fossil-rich limestone formed when freshwater snail shells piled up in fine lime mud. - Myth: The red Purbeck Marble slabs in old buildings came out of the quarry red. Fact: According to studies at Canterbury Cathedral, many of the red-looking slabs actually come from the green bed. The iron-rich mineral glauconite that makes the stone green oxidises to red after the stone has been laid. ## Did you know? - A Bronze Age stone burial chest (cist) made of Purbeck Marble was found at Langton Matravers. - An iron bell with two seats inside was found in old quarries near Langton Matravers; it is thought to have been used to lower quarrymen into the workings. - The 13th-century King's Table, once used at English coronations, is also made of Purbeck Marble. - Every Shrove Tuesday the Purbeck marblers gather at Corfe Castle to admit new apprentices to their company; then they play football in the street and kick the ball towards the old Ower Quay, where the stone was loaded onto boats in the Middle Ages. ## Where is it found? - Langton Matravers, Isle of Purbeck, Dorset, England (Type locality): England's earliest stone quarries, dating from Roman times, run along the valley side north of the village and were extended westwards to build the medieval cathedrals. The village museum tells the story of the quarrying. - Corfe Castle, Dorset, England (Historic source): In the Middle Ages the village had a large marble-carving and stone-cutting industry; the stone was sent across the country from Ower Quay in Poole Harbour. - Peveril Point, Swanage, Dorset, England (Known locality): The eastern end of the strip in which the Purbeck Marble beds cross the peninsula. - Worbarrow Tout, Dorset, England (Known locality): The western end of the strip in which the Purbeck Marble beds cross the peninsula. ## Sources - [Purbeck Marble](https://en.wikipedia.org/wiki/Purbeck_Marble), Wikipedia - [Purbeck Marble (building stones of Canterbury Cathedral)](https://www.canterbury-archaeology.org.uk/?p=673), Canterbury Archaeological Trust - [Sussex Marble](https://www.dorsetbuildingstone.org/sussex-marble.html), Dorset Building Stone - [Medieval marble quarries, Talbots Wood, Langton Matravers (MDO30751)](https://heritage.dorsetcouncil.gov.uk/Monument/MDO30751), Dorset Historic Environment Record - [Langton Matravers](https://dorsetlife.co.uk/?p=26585), Dorset Life - [Langton Matravers](https://en.wikipedia.org/wiki/Langton_Matravers), Wikipedia - [Corfe Castle (village)](https://en.wikipedia.org/wiki/Corfe_Castle_(village)), Wikipedia - [Shrove Tuesday Football Ceremony of the Purbeck Marblers](https://en.wikipedia.org/wiki/Shrove_Tuesday_Football_Ceremony_of_the_Purbeck_Marblers), Wikipedia - [Peveril Point](https://en.wikipedia.org/wiki/Peveril_Point), Wikipedia - [Worbarrow Bay](https://en.wikipedia.org/wiki/Worbarrow_Bay), Wikipedia - [Berriasian](https://en.wikipedia.org/wiki/Berriasian), Wikipedia - [Density of Solids](https://www.engineeringtoolbox.com/density-solids-d_1265.html), The Engineering ToolBox - [Limestone](https://geology.com/rocks/limestone.shtml), Geology.com Source: https://taslar.bumba.tr/en/stones/purbeck-marble/ · Licence: CC BY-SA 4.0