Sunday stone at the natural history museum

"Sunday stone" is an artificial stone composed of

calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ...

that formed on the walls of drainage pipes in some coal mines. It is striped due to the differing levels of coal dust produced during the day and night shifts. In some cases, a broader stripe is generated every seven days due to active mining not taking place on Sunday. Broader stripes would also appear when work stopped for other reasons. In one case, a broad stripe coincided with workers being given the day off to view a

cockfight Cockfighting is a blood sport involving domesticated roosters as the combatants. The first documented use of the word gamecock, denoting use of the cock as to a "game", a sport, pastime or entertainment, was recorded in 1634, after the term ...

. Breaks of more than a day would produce an even broader stripe, such as when Christmas fell on a Monday. The Sunday stone would over time block the drainage pipes necessitating their replacement. Where mines have improved ventilation, reducing the level of coal dust in the air, Sunday stone has ceased to be formed.

References

{{reflist Coal mining