Intricate sculpture

Coccoliths, and the related scales and sheaths, are characteristic features of a widespread group of organisms. The morphology of each structure is typical of each species and represents a range of extracellular objects from simple mineral-free plates to intrically sculptured, calcified and crystalline units fitted together to make a wreath or incrustation around the cell (for reviews see560,561 ). 

Either type of sculpture can be complex. If a sculpture is motionless, it can be constructed of many parts that are intricate and mysteriously joined together. In a kinetic sculpture, the element of motion leads to complexity. The sculpture must be arranged so the moving parts work together harmoniously. 

Brittle fracture is used for shaping and machining ceramics after they have been fired. Ceramics can be modified to make them machinable this is controlled fracture and is the approach we adopt with machinable glass-ceramics such as Macor (Chapter 26). Of course, many ceramics already are machinable and can be shaped into intricate and beautiful forms as illustrated in the carved marble sculpture shown in Figure 18.1. 

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