Carnelian is a brownish-red mineral commonly used as a semiprecious stone. Similar to carnelian is sard, which is generally harder and darker; the difference is not rigidly defined, and the two names are often used interchangeably. 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 ; and Thailand. It has been found in Indonesia, Brazil, India, Russia (Siberia), and Germany. In the United States, the official State Gem of Maryland is also a variety of carnelian called Patuxent River stone.

Susa was an ancient city in the lower Zagros Mountains about 250 km (160 mi) east of the Tigris, between the Karkheh and Dez Rivers in modern day Iran. One of the most important cities of the Ancient Near East, Susa served as the capital of Elam and the winter capital of Achaemenid Empire, and remained a strategic centre during the Parthian and Sasanian periods.