Optical Spectra of Epidote, Ca2(Al2Fe)[Si2O7][SiO4]O(OH) 


Optical Spectra of Clinozoisite, Ca2Al3[Si2O7][SiO4]O(OH) 


Optical Spectra of Piemontite, Ca2Al2Mn(Si2O7)(SiO4)O(OH)