Early clocks tended to be of iron, but clockmakers began to use brass in the 1570s.
Woods used for cases were typically oak, walnut or mahogany. Alternatively, a fruitwood or rosewood was used. Fruitwood was used because it carves superbly well. Ebony or ebonised wood was used to great effect on longcase clocks in the 1660s, and on spring driven table clocks (bracket clocks) into the 18th century.
Other materials use for cases include marble, ceramics, glass, slate, brass (carriage clocks).
Decoration may use inlay, marquetry, gilt metal (ormolu), enamel work (Champlevé or Cloisonné). Some absolutely fabulous carriage clocks have panels of Limoges. This is decorated glass from the Limoges area in France.
Sometimes dials and cases may be painted.
From the mid 17th century, most British clocks made significant use of wood in the case. They were relatively plain initially, but by 1680 there was some decorative marquetry work applied to longcases, as well as japanning. A variety of materials were used to achieve different effects. Marquetry and parquetry used stained bone, usually green for bird and floral patterns. Boxwood and ebony were used for stringing. Some of the clocks produced in England by, for example, John Ellicot in around 1750 were absolutely exquisite.
Continental clocks make much less use of wood than British clocks. Instead they are often of porcelain, marble, ormolu, or alabaster, heavily decorated with gilt. They tend to be much more ornate, especially in France.
The Dutch however made very elaborate and ornate wooden longcase clocks, very much like the English, but with their own distinctive characteristics.