These specimens were collected in an outcrop situated between the villages of Malpartida de Corneja and Casillas de Chicapierna, in Ávila. They are floating crystals of twinnen orthoclase (Karlsbad) those have been partially or totally pseudomorphized by quartz. They present visible forms of the twin, with altered faces with curious cavities. Some specimens still preserve an orthoclase crystal core. This pseudomorphosis is very unusual.