Alabaster is a rare, fine-grained, semi-translucent form of gypsum (hydrous calcium sulphate), created from marine salts. It is a stone found in solid masses under the ground, frequently in oval shaped blocks.
Once quarried across Europe, alabaster actually takes its name from the Egyptian town of Al-Abastron, where a similar looking, but geologically quite different, stone had been quarried since ancient times (usually referred to as ‘calcite’ alabaster). This “Oriental” alabaster was highly esteemed for making small perfume-bottles or ointment vases called ‘alabastra’, and this is perhaps the origin of the name.
It is a soft stone - its ‘hardness’ ranges between 1.5 and 2.5 on the Mohs scale (1 = very soft, eg talc, and 10 = very hard, eg diamond). Because of its softness, it scratches easily. Some alabasters can even be scratched with a finger nail. A minor knock can also ‘bruise’ the stone, producing an exaggerated whiteness at the site.
Plaster of Paris is formed from gypsum (alabaster is a fine-grained form of gypsum) and water - when the dry powder absorbs water it forms a paste which then hardens.
Alabaster stone too will absorb water, and sculptures, therefore, are not suitable for leaving out of doors, as they will discolour and partially dissolve.
The colours, veining and texture of this translucent stone make it highly suitable for small-scale and figurative sculptures. There are numerous varieties of alabaster, and its appearance changes according to the local geology. The various colours are produced when other substances, especially clay and metal oxides, most commonly of iron, are included. The commonest colour is grey, produced by its clay inclusions.
Alabaster in England
Alabaster carving was once a thriving trade in England. In the 14th and 15th centuries, the alabaster was used mainly for icons and altarpieces, and for funerary effigies.
It was quarried in South Derbyshire, Nottingham and parts of Staffordshire. Seams of alabaster can be seen today in certain cliffs of North Somerset, appearing as bands or veins.
Most sculptors, or ‘alabasterers’, in medieval times were based in Nottingham and Burton-on-Trent.
Alabaster in Italy
In Italy, alabaster is found mainly around Volterra. This alabaster is considered to be the best in Europe on account of its distinctive features - a translucent, velvety and often veined alabaster. A small alabaster industry continues at Volterra, mainly for the tourist market.