Yizuan cabochon cushion natural chalcedony stone natural yellow dyed agate stone

Carnelian is a brownish-red mineral commonly used as a semi-precious gemstone. Similar to carnelian is sard, which is generally harder and darker. Both carnelian and sard are varieties of the silica mineral chalcedony colored by impurities of iron oxide. The color can vary greatly, ranging from pale orange to an intense almost-black coloration. Significant localities include Yanacodo, Peru; Ratnapura, Sri Lanka; and Thailand. It has been found in Indonesia, Brazil, India, Russia, and Germany.

Agate is a common rock formation, consisting of chalcedony and quartz as its primary components, with a wide variety of colors. Agates Stone are primarily formed within volcanic and metamorphic rocks. The ornamental use of agate dates back to Ancient Greece in assorted jewelry and in the seal stones of Greek warriors. Use of beads necklaces with pierced and polished agate goes further back to the 3rd millennium BCE in the Indus Valley civilisation.

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.