First known occurrence of inyoite in a playa, at Laguna Salinas, Peru

Inyoite, Ca2B6O11·13H2O, is here reported as a primary mineral which formed simultaneously with the enclosing mud of a playa, rather than by alteration of an earlier borate mineral. It occurs near the surface at Laguna Salinas, east of Arequipa, Peru, as crystal aggregates in a bed of black mud which also contains ulexite nearer the surface. A bed of white volcanic ash lies just under the surface efflorescence and above the ulexite-bearing mud.