# Bath stone - Page: https://taslar.bumba.tr/en/stones/bath-stone/ - Turkish: Bath taşı - Also known as: Bath Oolite, Great Oolite Freestone, Bath freestone - Kind: Rock - Classification: Rocks › Sedimentary rocks › Chemical and biochemical - Hardness (Mohs): 3 - Specific gravity: 2–2.5 g/cm³ - Colours: honey, golden buff, pale buff, cream - Composition: Oolitic limestone: mostly calcium carbonate, made of small round grains called ooids bound by crystalline calcite (sparry) cement, mixed with shell, crinoid and coral fragments. There is little fine lime mud between the grains. - Texture: Medium- to coarse-grained; under a hand lens the fish-roe-like ooids (about 0.25–2 mm) can be seen. With no strong grain direction it is a “freestone” that can be cut in any direction; it is quite porous. - Value ladder: 4/9 step, Fine dimension stone and ore The stone that turned a whole city golden: the honey-coloured oolitic limestone of Georgian Bath, the Royal Crescent and Buckingham Palace. Bath stone is a honey- to golden-coloured oolitic limestone quarried in south-west England, in the area between Bath, Bradford-on-Avon and Corsham. It is made of small, fish-roe-like grains of lime, and because it can be cut easily in any direction it is a “freestone” much loved by masons. Used since Roman times, it gave the Georgian buildings of Bath, now a UNESCO World Heritage city, their character in the 18th century. ## How does it form? In the Middle Jurassic, the Bath area lay beneath a warm, shallow sea. On the seabed, tiny shell fragments and sand grains rolled by waves and currents grew into round grains called **ooids** as layer after layer of lime settled on them. These grains piled up in thick beds together with fragments of shells and crinoids; then the spaces between them filled with crystalline **calcite** cement and the sediment hardened into rock. Bath stone belongs to the Chalfield Oolite Formation in the rock sequence geologists call the **Great Oolite Group**, especially its Combe Down Oolite and Bath Oolite members. Because there is little mud between the grains and no strong grain direction, the stone can be sawn in any direction; masons call such stones **freestones**. Freshly quarried stone contains moisture known as “quarry sap”, which makes it soft and easy to work; it hardens as it dries. ## What is it used for? - **Roman and medieval times:** It was used in Roman villas at Box and Bathford and in parts of the Roman baths at Bath. In the Middle Ages it went into Lacock Abbey, and later into Longleat House. - **Georgian Bath:** In the early 18th century the postmaster Ralph Allen bought the quarries at Combe Down and promoted the stone; the architect John Wood and his son designed buildings such as the Royal Crescent and the Circus in it. Pulteney Bridge and Bath Abbey are of Bath stone too. Today the whole city is a UNESCO World Heritage Site. - **Across the country and the world:** The Kennet and Avon Canal (1794–1810) and the Great Western Railway made it easier to ship the stone to London. Buckingham Palace, Lancaster House, Apsley House, the Royal Pavilion in Brighton and, abroad, Cape Town City Hall all use it. - **Today:** It is used for walling, ashlar facades, window and door surrounds, fireplaces and sculpture. It is not recommended for floors, because it wears quickly. ## Where is it found? Bath stone is quarried on the border of Somerset and Wiltshire, in the area between **Bath**, **Bradford-on-Avon** and **Corsham**. The main old quarries and mines were around **Combe Down**, **Bathampton Down**, **Box**, **Monkton Farleigh** and **Limpley Stoke**. Most of the stone was mined underground in chambers, with pillars left to hold up the roof; at Box, digging began in Roman times and went on until 1968. Demand fell in the economic depression of the 1930s, many quarries were handed over to the military in the Second World War, and the industry never fully recovered. Today the stone is taken mainly from underground quarries around Corsham, such as Hartham Park and Monk's Park, and Stoke Hill mine is also still worked. ## How to recognise it - Its colour ranges from honey yellow through pale buff to cream, and it glows golden in sunlight. - Under a hand lens, small round grains (ooids) like fish roe can be seen on the surface; the texture is distinctly sandy. - Freshly quarried stone is damp and easy to work; it hardens as it dries. - Being a limestone, it fizzes in dilute acid and is easily scratched by a steel knife. ## Fakes and imitations - Portland stone from Dorset is also an oolitic limestone and is confused with Bath stone, but Portland stone is younger (Late Jurassic) and white-grey. - The name Bath stone covers not one quarry but stone of varying quality from many quarries in the same area; “Box Ground”, for example, is counted among the densest and most durable kinds. ## What determines its value? As a building stone, its value depends on the warmth and evenness of its colour, whether large, crack-free blocks can be extracted, how easily it can be worked and how well it stands up to the weather. Denser, more durable kinds are preferred for outside walls, softer ones for interiors and carving. Because most old quarries have closed, finding stone that matches the colour and texture of historic buildings for repairs is hard, which makes suitable blocks valuable. This information is educational, not buying, selling or investment advice. Value varies enormously with quality and treatment. ## Myths and misconceptions - Myth: Bath stone is quarried in the city of Bath. Fact: Most Bath stone comes from outside the city, from a triangle of about 20 square miles between Bath, Bradford-on-Avon and Corsham. Most of the working quarries today are around Corsham in Wiltshire. - Myth: Portland stone and Bath stone are the same stone. Fact: Both are oolitic limestones, but they differ in age and place: Bath stone is Middle Jurassic and honey-coloured, while Portland stone is Late Jurassic, white-grey and comes from the Isle of Portland in Dorset. ## Did you know? - The Bathonian stage of the geological time scale (about 168–166 million years ago) is named after the city of Bath. - During the Cold War, old underground quarries at Corsham were turned into a secret government headquarters meant to shelter nearly 4,000 people, including the Prime Minister and Cabinet, in a nuclear war. - Because the old Combe Down mines threatened to collapse just a few metres beneath houses, they were filled with more than 400,000 cubic metres of foamed concrete between 1999 and 2009. - Bath stone did not stay in England: Cape Town City Hall in South Africa and Union Station in Washington were also built with it. ## Where is it found? - Combe Down and Bathampton Down Mines, Bath, Somerset, England (Type locality): Mines worked in the 18th century by Ralph Allen, dug by the room-and-pillar method, which ran for about three hundred years. They were stabilised with foamed concrete between 1999 and 2009. - Box Mine, Wiltshire, England (Historic source): A network of tunnels begun in Roman times; stone extraction ended in 1968. Today it is an important winter roost of greater horseshoe bats. - Corsham (Hartham Park and Monk's Park quarries), Wiltshire, England (Major deposit): The main district where Bath stone is still mined underground. During the Second World War and the Cold War the old quarries served as ammunition stores and an underground headquarters. - Monkton Farleigh, Wiltshire, England (Historic source): In the 19th century Bath stone quarrying was the parish's main employer; from the late 1930s its underground quarries were turned into one of the country's largest ammunition stores. - Limpley Stoke, Wiltshire, England (Known locality): St Stephen's Church in Bath is built of limestone from here. ## Sources - [Bath stone](https://en.wikipedia.org/wiki/Bath_stone), Wikipedia - [Geology of the Bath area: Applied geology: building stone and bulk minerals](https://earthwise.bgs.ac.uk/index.php/Geology_of_the_Bath_area:_Applied_geology:_building_stone_and_bulk_minerals), British Geological Survey (Earthwise) - [Great British Stone: Bath Stone](https://www.stonespecialist.com/news/stone-heritage/great-british-stone-bath-stone), Stone Specialist - [Box Ground Bath Stone: it's back](https://stonespecialist.com/news/stones-quarries/box-ground-bath-stone-its-back), Stone Specialist - [Combe Down Limestone](https://stonelibrary.shu.ac.uk/combe-down-limestone/), Sheffield Hallam University Stone Library - [Combe Down and Bathampton Down Mines](https://en.wikipedia.org/wiki/Combe_Down_and_Bathampton_Down_Mines), Wikipedia - [Box Mine](https://en.wikipedia.org/wiki/Box_Mine), Wikipedia - [Corsham](https://en.wikipedia.org/wiki/Corsham), Wikipedia - [Monkton Farleigh](https://en.wikipedia.org/wiki/Monkton_Farleigh), Wikipedia - [Limpley Stoke](https://en.wikipedia.org/wiki/Limpley_Stoke), Wikipedia - [Portland stone](https://en.wikipedia.org/wiki/Portland_stone), Wikipedia - [Limestone](https://geology.com/rocks/limestone.shtml), Geology.com Source: https://taslar.bumba.tr/en/stones/bath-stone/ · Licence: CC BY-SA 4.0