Onyx Marble in the Quarry
WHAT TYPE OF ONYX IS USED
The term Onyx is used to define both a type of marble (sardonyx) and a semi-precious stone, agate. True onyx or agate, is a very hard ornamental stone which consists of a hard variety of chalcedony (quartz), typically banded in appearance and used to make jewellery.
Onyx marble is not as hard as agate but much harder than common marble which makes it more difficult to process. Onyx marble has a distinct light transmission character which allows light to transfer through the onyx marble up to a thickness of 4cm. Onyx marble is available in white, yellow, green and red colour tones.
Onyx Marble Blocks in the Field
CARVING THE ONYX
The carving of Onyx marble to make decorative objects started in Cappadocia in Turkey where it was known as "Hacibektas Tasi" (a culturally important town in the region). Early production in the region employed more primitive techniques, but today techniques have been improved and onyx marble carving spread to other regions in Turkey after the 1960s.
Onyx marble is used to make various decorative objects such as vases, ashtrays, pen holders, sugar bowls, candle holders, trinkets, statues of animals and chess sets. The raw material onyx marble is available and quarried in the cities of Nevsehir , Kirsehir , Balikesir, Bilecik, Ankara and Tokat.
There are four successive stages of Onyx marble carving. These are cutting, shaping and styling, polishing and fine polishing.
Cutting the Onyx Marble Block
THE CUTTING PROCESS
During the Cutting Process, blocks of Onyx marble are brought to the workshops from the quarry to be cut to smaller sizes suitable for the items to be carved. Diamond-tipped circular saw blades are used in the lathe bench to cut the blocks of onyx marble. During cutting a continuous water jet is used to prevent dust formation and reduce friction between the diamond blade and onyx marble.
Carving the Onyx Marble
SHAPING AND STYLING
During the Shaping and Styling process, the smaller onyx marble blocks are given their forms and styles on the lathe benches. A small wedge is lodged at each end of the onyx marble block to hold it in place during the shaping process and is cut off once the block has achieved its desired style. Shaping the hard rotating onyx marble block in the lathe requires a lot of skill and hard work and many hand tools are utilised including chisels, set squares, hook punches, rasp and files.
Shaping and Styling the Onyx Marble
During the Polishing process, the final shape and style of the item is achieved in the styling lathe. The ancillary wedges that were used to attach the blocks to the spinning machine are cut off and the items are moved onto another lathe bench for polishing. Wedges are again used to hold the shaped items in the polishing lathe to prevent damage by the lathe bench during spinning. To remove the surface roughness and give a smooth finish, items are sanded using carbon block, sandpaper and water.
Polishing the Onyx Marble
Fine Polishing is the final stage of the carving of onyx marble, where the polished items achieve their glossy look. The identity of the polishing agent is treated as a trade secret, however oxalic acid is known to be used.