Raspberry-red grossular from Sierra de Cruces Range, Coahuila, Mexico
Geiger, Charles A.; Stahl, Andreas; Rossman, George R.
European Journal of Mineralogy Volume 11 Number 6 (1999), p. 1109 - 1114
published: Nov 29, 1999
manuscript accepted: May 18, 1999
manuscript received: Dec 4, 1998
ArtNo. ESP147051106018, Price: 29.00 €
Abstract A raspberry-red grossular from the Sierra de Cruces Range in the state of Coahuila in Mexico has been investigated. Electron-microprobe analysis and 57Fe Mössbauer and UVYVIS spectroscopy were used in order to investigate the nature of the unusual red colour. The composition of the garnet is approximately (Ca2.94Mg009Mn2+0.10)313(Al1.90Fe3+0.05Mn3+0.01)1.96Si2.97O12. The UV/VIS spectrum is characterised by an absorption envelope centred around 19,000 cm1 in the green region, which can be fitted with two bands located at 19,503 and 17,302 cm-1, originating from two spin-allowed dd-electron transitions. They result from the presence of Mn3+ on the octahedral site of point symmetry 3¯.