A magnesium analogue of chalcophanite in manganese-rich concretions from Baja California

Russel M. Potter and George R. Rossman

 Division of Geological and Planetary Sciences
California Institute of Technoogy
Pasadena, CA  91125


Concretions which carry chemical remanent magnetization in sediments in Baja Califor­ nia, Mexico, previously called "hydropsilomelane," were found to consist of siltstone matrix minerals cemented by a manganese oxide. The X-ray powder pattern, infrared spectra, and chemical analyses indicate that the manganese oxide has the chalcophanite structure. The high concentration of magnesium, presumed to occur in the interlayer position of this min­ eral, suggests that it is the magnesium  analogue of chalcophanite and extends the known range of substitution in chalcophanite-structure minerals.

last updated: 5-Oct-2020