Study on Mineralogical Characteristics of Chlorite Jade from Russia

The gemmological characteristics, microstructure and mineralogical characteristics of a newkind of chlorite jade—“seraphinite”— from Russia, which is recently presented in the gem markets, are studied by using refractometer, ultraviolet fluorescence lamp, X-ray diffraction (XRD) and scanning electron microscope (SEM). The results showthat the chlorite jade is in dark green, semi-translucent to opaque, and lepidoblastic texture, with hardness of 2.5, refractive index 1.58 and density 2.60 g/cm³. It has homogeneous texture and less fissures, and no fluorescence under ultraviolet fluorescence lamp. XRD analysis shows that the mineral composition of the chlorite jade is mainly chlorite. SEM results showthat the chlorite exhibits well-developed crystal. It also can be seen that the chlorite aggregates in different directions showa crossed distribution. The chemical analysis suggests that the chlorite contains w(MgO) 35.4%, w(Al₂O₃) 14.8%, w(SiO₂) 32.6 %, w(FeO) 4.2% and w(H₂O) 13.0%. The jade is composed of almost clinochlore, with a chemical formula Mg₆(Fe_0.7Mg_3.8Al_1.5) (Si_6.2Al_1.8) O₂₀(OH) 16. The chlorite crystal is in oriented distribution. In addition, the large particles of the schistose crystals exhibit wave-shaped bending. Both the microstructure and mineralogical characteristics are probably responsible for silky luster of the chlorite jade.