Works of art are material and materials have meaning. They determine form, style, and effect and are often chosen intentionally by artists to convey artistic ideas and reinforce expressive effects. An artist's choice of materials both limits and opens up technical possibilities. Depending on their geographical occurrence, rarity or composite nature, materials are valued, compared and imitated; processes that stimulate innovation in the arts. Materials are also charged with manifold cultural connotations, conveying power, beauty, splendor or humbleness. Despite the richness of the topic, the...