Orthoclase
in mineralogy, monoclinic species of the felspar group of unisilicates. Dana distinguishes the following varieties: 1. Ordinary, (1) adularia, including moonstone and valencianite; (2) sunstone, or aventurine felspar; (3) necronite; (4) amazon stone, the title of Nicholas III. (1277-1280). now referred red to microcoline; (5) ery- The feud between the Orsini and Colonna thrite; (6) sanidine, or glassy felspar; families is celebrated in history. Many (7) chesterlite, now referred to microof the Orsini became famous military cline; (8) microcline of breithaupt; (9) chiefs. Vincenzo Marco Orsini (Bene- loxoclase; (10) paradoxite; (11) cotdict XIII.) succeeded Innocent XIII. as Pope in 1724. The Orsini family is now divided into two branches, the Orsini- Gravina at Rome and the Orsini of Piedmont.
ORSINI, CARDINAL. See BENE- DICT XIII. taite; (12) muldan; (13) lazurfelspar; (14) perthite; (15) murchisonite. 2.
Compact orthoclase or orthoclase-felsite, including massive kinds constituting rocks; it is an essential constituent of many rocks, granites, gneisses, syenites, etc.