Chalcedony is a polycrystalline form of silica, composed of very fine inter growths of quartz and moganite. Chalcedony’s standard chemical structure is SiO2 (Silicon Dioxide).

Chalcedony has a waxy luster. It may be semitransparent or translucent. It can assume a wide range of colors, but the most commonly seen are white to gray, grayish-blue and a shade of brown ranging from pale brown to nearly black.

In the Bronze age, chalcedony was in use in the Mediterranean region. Some chalcedony seals recovered date back to 1800 B.C. People living along the Central Asian trade routes used various forms of chalcedony, to carve intaglios, ring bezels with the upper faceted portion of a gem projecting from the ring setting and beads that show strong Greece-Roman influence.

Hot wax would not stick to it so it was often used to make seal impressions.
Originally the agate carving industry around Idar and Oberstein was driven by local deposits that were mined in the 15th century. In the 19th century Idar-Oberstein became the world’s largest chalcedony processing center, in particular agates. Most of these agates were sourced in Latin America, in particular Brazil.

Several factors contributed to the re-emergence of Idar-Oberstein as agate center of the world. Ships brought agate nodules back as ballast providing cheap transport. Cheap labor and a superior knowledge of chemistry which allowed them to dye the agates in any color using well guarded secret methods helped.

Each mill in Idar-Oberstein had four or five grindstones. These were of red sandstone and two men usually worked together at the same stone.