NEW STRUCTURAL AND SPECTROSCOPIC DATA FOR EOSPHORITE

X-ray diffraction refinement of the crystal structure of eosphorite ha s been carried out with reference to the orthorhombic space group Cmca . The structure is similar to that previously described by Hanson (196 0), but the standard deviations are improved. Optical absorption and p hotoluminescence have also been studied for this mineral. Two sharp em ission lines, denoted as R1 and R2, superimposed to a broad band (630- 750 nm) have been related to the presence of Cr3+ ions. The excitation spectrum of these emissions confirms that the absorption (excitation) bands centred at 431 nm and 585 are related to with 4A2 --> 4T1 and 4 A2 --> 4T2 spin allowed transitions of this ion.