A generic term applied to a type of clock first manufactured in France towards the end of the 19th century. While true marble has long been used for clock cases, the so-called 'marble' clock has a case made mainly from slate with a high surface polish. These cases are very heavy and provide great stability to pendulum clocks; this, combined with their excellent movements, gives long and satisfactory timekeeping. Ornamentation with true marble may be found in elaborate cases, combined with gilt metal pillars and medallions. One disadvantage of slate is its tendency to chip. It is dangerous to lift marble clocks except by the base, for the case may break apart under its own weight. The surface polish is easily damaged by water and is very difficult to restore. Recently despised, these clocks are now rapidly appreciating in value.