page_title: Chalcedony
section_title: Carnelian
hierarchical_section_title: Chalcedony / Varieties / Carnelian
caption_attribution_description: Two polished pebbles of carnelian/sard. Scale is in millimeters.
context_page_description: Chalcedony is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic. Chalcedony's standard chemical structure is SiO₂.
  Chalcedony has a waxy luster, and may be semitransparent or translucent. It can assume a wide range of colors, but those most commonly seen are white to gray, grayish-blue or a shade of brown ranging from pale to nearly black. The color of chalcedony sold commercially is often enhanced by dyeing or heating.
  The name chalcedony comes from the Latin chalcedonius. The name appears in Pliny the Elder's Naturalis Historia as a term for a translucid kind of Jaspis. The name is probably derived from the town Chalcedon in Asia Minor. The Greek word khalkedon also appears in the Book of Revelation. It is a hapax legomenon found nowhere else, so it is hard to tell whether the precious gem mentioned in the Bible is the same mineral known by this name today.
context_section_description: Carnelian (also spelled cornelian) is a clear-to-translucent reddish-brown variety of chalcedony.  Its hue may vary from a pale orange, to an intense almost-black coloration.  Similar to carnelian is sard, which is brown rather than red.
caption: Carnelian
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