R0119 Cave Pearl - Great Oolite mine, England
A section through a 'cave pearl'. These form in shallow pools in mines and caves from calcite/aragonite precipitating around a nucleus. Continuous movement of the 'pearl', either by water dropping on it or water flowing slowly through the pool, allows precipitation in concentric layers around the whole nucleus - hence the 'pearl'. Eventually the 'pearl' may get too large to be moved around by the water at which point precipitation may only occur on its upper surface effectively turning it into a stalagmite. That's what happened in this case. This is from the floor of a Great Oolite mine - one of the mines used to supply Bath Stone (the stone used to build Bath). It is about 5 cm across.
R0119 Cave Pearl - Great Oolite mine, England
A section through a 'cave pearl'. These form in shallow pools in mines and caves from calcite/aragonite precipitating around a nucleus. Continuous movement of the 'pearl', either by water dropping on it or water flowing slowly through the pool, allows precipitation in concentric layers around the whole nucleus - hence the 'pearl'. Eventually the 'pearl' may get too large to be moved around by the water at which point precipitation may only occur on its upper surface effectively turning it into a stalagmite. That's what happened in this case. This is from the floor of a Great Oolite mine - one of the mines used to supply Bath Stone (the stone used to build Bath). It is about 5 cm across.