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.  Carnelian is a 7 on the Mohs scale.  Carnelian is thought to relieve lethargy, depression, low self-esteem, fear and anxiety. Also carnelian is believed to increase inner self understanding.