CHALCEDONY (GEODE) (large cabinet)

Chalcedony is a cryptocrystalline variety of silica, characterized by its fine intergrowths of quartz and moganite, two silica minerals that differ in crystal structure—quartz being trigonal and moganite monoclinic. Its chemical composition is primarily silicon dioxide (SiO2). This mineral exhibits a waxy luster and can be either semitransparent or translucent, displaying a spectrum of colors, with the most common hues being white, gray, grayish-blue, and various shades of brown, from light to nearly black. Commercially available chalcedony often undergoes color enhancement through dyeing or heating. The term "chalcedony" is derived from the Latin word chalcedonius, likely linked to the ancient town of Chalcedon in Asia Minor. Historical references to chalcedony can be found in Pliny the Elder's Naturalis Historia, where it is described as a translucent form of jaspis, and in the Book of Revelation, which mentions a gem called khalkedón, though its exact identity remains uncertain. Additionally, the term "plasma" is sometimes used to describe green translucent chalcedony.