Ore

Gold, silver, and copper artifacts left by prehistoric tribes and ancient civilizations attest to an interest in ores extending back to earliest times. Indeed, human history is divided into chalcolithic (copper-stone), bronze, iron, and atomic (uranium) ages based on the use of metals. In spite of this, little was known about the origin of ore until relatively recent times. Greek philosophers believed that metallic veins were living things with roots at depths and near-surface branches of different metals. Astrologers contended that gold, silver, iron, and mercury were formed under the influence of the Sun, Moon, Mars, and Mercury.

The first major break from this line of thinking came in 1556 with the publication of De Re Metallica by a German physician writing under the Latinized pen name of Georgius Agricola. Agricola's keen observations and naturalistic explanations marked a departure from the speculations of the ancients. His work remains a Renaissance Age classic, and Agricola is recognized as the father of economic geology.

Major advances in the study of ore deposits were made following the discovery and development of the many great metal-bearing veins in the western United States. An outgrowth of this period was a belief that ores are related to emanations given off by cooling igneous rocks. Although still considered a process of great significance, sedimentary and metamorphic processes are also recognized as important.