glossary
Marble - This is formed when limestone (see below) undergoes metamorphic recrystalisation caused by intense pressure and/or heat over a long period of time. All the marble I have used comes from Carrara in Italy (as shown in the photo), the most famous source of marble for sculptors and much loved by Michelangelo. The Carrara quarries have been in operation for over 2000 years. The stone is white but may contain variable gray banding in places. This marble comes from the Lower Jurassic period, about 150 million years ago.Purbeck Marble (limestone) - When the Romans discovered this stone in Dorset (c. AD 200), they called it Marble because of the high level of shine when polished. It was used for the building of cathedrals (eg Salisbury) and the like for many years, but is now in short supply. It all comes from a small area near Swanage (including St Andhelm's quarry - see photo) and is a limestone full of shells. It was formed in a warm fresh water lagoon some 140 million years ago, mainly from millions of fresh water snails (oviparous shells) - hence the wonderful colours. The predominant colour is typically blue, but it can also be green.
Other Limestones - these are made predominantly of calcium carbonate, formed from the skeletons and shells of sea creatures falling to the sea floor and over time compressing to form stone. It typically takes about 1,000 years to develop 1 inch thickness of stone. Besides Purbeck Marble (above), I have worked with a variety of limestones, differing in colour and fossil content, and all from the Upper Jurassic period (typically 140 to 160 million years ago):
Purbeck/Portland Spangle - Greyish; large fossils, (oyster shells mainly), crystalline.
Purbeck Grub - Bluish/brown/grey, dense fossil content.
Portland and Purbeck Freestone - Creamy-white, almost free of obvious fossils.
Hopton Wood - pinkish, some fossil content, from Hopton Wood quarry near Matlock, Derbyshire.
Serpentine - this covers a wide range of stone, and is typical of the stone used in Zimbabwean sculpture. They are metamorphic (like marble), having originally been laid down on a sandy sea floor and then transformed over millions of years by intense heat and pressure. I have used a wide range of Serpentine stone, ranging below from hardest to softest:
Zimbabwean Springstone
Zimbabwean Opal
Indian Green Springstone
Indian Red Springstone