# Petit Granit

- Page: https://taslar.bumba.tr/en/stones/petit-granit/
- Turkish: Petit granit
- Also known as: Belgian blue stone, Pierre bleue de Belgique, Belgian Blue Limestone, Arduin, Nero Belga, Belgian Granite
- Kind: Rock
- Classification: Rocks › Sedimentary rocks › Chemical and biochemical
- Hardness (Mohs): 3
- Specific gravity: 2.67–2.7 g/cm³
- Colours: grey, bluish grey, blue-black, shiny black when polished, light grey when weathered
- Composition: A limestone packed with the remains of sea lilies (crinoids): about 96 percent calcite, with traces of dolomite, quartz and pyrite. The very fine-grained lime matrix that binds the fossils carries finely divided carbon, which gives the dark colour. Fragments of brachiopod shells, bryozoans and corals also occur.
- Texture: Dense and almost non-porous (porosity about 0.4 percent by volume); the cleavage faces of the crinoid fragments sparkle in the light. Geologists class it as a packstone, sometimes a grainstone, or a biomicrite.
- Value ladder: 4/9 step, Fine dimension stone and ore

Called “little granite” but not granite at all: Belgium's blue limestone, packed with sea-lily fossils, that polishes to a shiny black.

Petit Granit is a dense, bluish-grey limestone quarried in Wallonia, Belgium, in the Soignies-Écaussinnes basin and the Condroz. It formed about 350 million years ago, in the Carboniferous, from the remains of sea lilies (crinoids) that lived in a shallow sea. Despite its name it has nothing to do with granite. It turns shiny black when polished and has been used in Belgium's buildings, sculpture and gravestones since the Middle Ages.

## How does it form?

Petit Granit formed early in the Carboniferous, late in the Tournaisian stage (about 350 million years ago). At that time southern Belgium lay beneath a warm, shallow sea. On the seabed, **sea lilies** (crinoids), animals with stalks and arms that look like flowers, spread like meadows. When they died, their limy skeletons fell apart into small discs. These piled up in thick beds together with brachiopod shells, bryozoans and pieces of coral.

The spaces between the fragments filled with lime mud carrying finely divided carbon, and as the mud hardened, the debris was bound tightly into a dense limestone. It is this carbon that gives the stone its blue-black colour. Each crinoid fragment behaves like a single calcite crystal, so when the stone is broken their cleavage faces glint in the light.

## What is it used for?

- **Architecture:** Since the Middle Ages it has been used in many Belgian buildings, especially in Brussels. Seneffe Castle, the church of Sainte-Waudru in Mons and the Church of St. Joseph in Brussels are among them. Abroad, it went into the Panthéon and Notre-Dame Cathedral in Paris, St. Michael's Church in Aachen and Funchal Cathedral on Madeira. Modern buildings such as Liège-Guillemins station use it too.
- **Façades and floors:** It is used for facing slabs, door and window sills, columns, stairs, indoor and outdoor paving, kitchen worktops and fireplaces.
- **Gardens and streets:** It is chosen for paving setts, kerbs, wall coping, fountains and benches.
- **Sculpture and monuments:** Because it is easy to work and polishes to a black shine, sculptors and monumental masons use it widely. Käthe Kollwitz's “The Grieving Parents” and the 1592 coat of arms of Liège are carved from it.

## Where is it found?

Petit Granit is quarried only in Belgium, in Wallonia. The oldest and best-known basin is around **Soignies** and **Écaussinnes** in the province of Hainaut. Quarry records at Soignies go back to about 1400, and the Gauthier-Wincqz quarry there has been worked without interruption since the 17th century. In the province of Liège, quarries in the Ourthe valley and the Condroz, around **Sprimont**, **Anthisnes** and **Ouffet**, produce stone of the same age. Sprimont's old power station of 1904 is now a museum of stone. About 15 quarries are working in the region today.

## How to recognise it

- It is grey, bluish grey or blue-black; polished it turns shiny black, and outdoors it slowly fades to light grey.
- Pale remains of sea lilies, looking like tiny rings and stem pieces, stand out in the dark matrix.
- On a fresh break, the cleavage faces of the fossils sparkle in the light.
- Being a limestone, it fizzes in dilute acid and can be scratched with a steel knife; true granite does neither.

## What determines its value?

As a building stone, its value depends on the depth and evenness of its colour, its high compressive strength, its low porosity and frost resistance, and whether large, crack-free blocks can be quarried. Its ability to take very different finishes, polished, flamed, chiselled or bush-hammered, widens its uses. The appellation of origin and technically approved quarries guarantee where the stone comes from.

This information is educational, not buying, selling or investment advice. Value varies enormously with quality and treatment.

## Myths and misconceptions

- Myth: Petit Granit is a kind of granite. Fact: Although its name means “little granite”, Petit Granit is a limestone: a sedimentary rock made of sea-lily fossils that fizzes in acid. Granite is an igneous rock of quartz and feldspar formed when magma cools deep underground.

## Did you know?

- In 2017 the International Union of Geological Sciences (IUGS) designated Petit Granit a Global Heritage Stone Resource.
- The stone's dark colour comes from finely divided carbon in its matrix. As rain washes the carbon from the surface, the stone lightens and takes on a pale grey patina.
- In Belgium, use of the name “Petit Granit” is protected by a local appellation of origin (Appellation d'Origine Locale).
- Since the 18th century the stone has been exported, mostly to the Netherlands but also to France and Germany, and later around the world; it was even used in the original installations of the Suez Canal.

## Where is it found?

- Soignies (including Neufvilles), Hainaut, Belgium (Type locality): The first quarries in the archives date from about 1400, and the Gauthier-Wincqz quarry has been worked without interruption since the 17th century. The Clypot quarry at Neufvilles lies in the same basin.
- Écaussinnes, Hainaut, Belgium (Major deposit): The Tellier des Prés quarry, on the boundaries of Soignies, Braine-le-Comte and Écaussinnes, opened in 2008 and is gradually taking over from the nearly exhausted Soignies quarry.
- Sprimont (Chanxhe, Coreux and Rondia quarries), Liège, Belgium (Major deposit): The quarries were revived around 1880; the old power station of 1904 is now a museum of stone.
- Anthisnes, Condroz, Liège, Belgium (Known locality)
- Ouffet (Troydo quarry), Condroz, Liège, Belgium (Known locality): Worked for blocks since the 1930s; the workable seamless beds are about 30 metres thick.

## Sources

- [Petit Granit](https://en.wikipedia.org/wiki/Petit_Granit), Wikipedia
- [Petit granit (pierre bleue)](https://fr.wikipedia.org/wiki/Petit_granit), Wikipédia (fr)
- [Petit Granit – Pierre bleue de Belgique (Global Heritage Stone Resource)](https://iugs-geoheritage.org/geoheritage_stones/petit-granit-pierre-bleue-de-belgique/), IUGS Subcommission on Heritage Stones
- [NIT 228 Pierres naturelles — fiche Petit Granit](https://www.buildwise.be/media/mqehyekm/petit-granit-en.pdf), CSTC / Buildwise
- [Les carrières de la Pierre Bleue Belge S.A. — Petit granit, Belgian blue limestone (technical sheet)](https://www.pierresetmarbres.be/wp-content/uploads/2021/01/pm1703-fiche-pbb-2018-uk-v02a.pdf), Pierres et Marbres de Wallonie, 2018
- [The Sprimont Quarries — Petit granit, Belgian blue limestone (technical sheet)](https://www.pierresetmarbres.be/wp-content/uploads/2021/01/pm1703-fiche-sprimont-2018-uk-v02a.pdf), Pierres et Marbres de Wallonie, 2018
- [Pierre Bleue de Wallonie — Petit granit, Belgian blue limestone (technical sheet)](https://www.pierresetmarbres.be/wp-content/uploads/2021/01/pm1703-fiche-pbw-2018-uk-v03c.pdf), Pierres et Marbres de Wallonie, 2018
- [Soignies](https://en.wikipedia.org/wiki/Soignies), Wikipedia
- [Écaussinnes](https://en.wikipedia.org/wiki/%C3%89caussinnes), Wikipedia
- [Sprimont](https://en.wikipedia.org/wiki/Sprimont), Wikipedia
- [Anthisnes](https://en.wikipedia.org/wiki/Anthisnes), Wikipedia
- [Ouffet](https://en.wikipedia.org/wiki/Ouffet), Wikipedia
- [Limestone](https://geology.com/rocks/limestone.shtml), Geology.com


Source: https://taslar.bumba.tr/en/stones/petit-granit/ · Licence: CC BY-SA 4.0