Chalcedony (/kælˈsɛdəni/, kal-SEH-də-nee, or /ˈkælsədoʊni/, KAL-sə-doh-nee) 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.

Category: Oxide minerals, quartz group

Crystal system: Trigonal or monoclinic

Diaphaneity: Translucent