The Gemological Characteristics And Color Origin Of “Dushan Jade” In Philippines

Recently,a new variety of jade has appeared in the Shifosi Marke.Businessmen call it"Dushan Jade"in Philippines.Several conventional gemological tests have been carried out based on the purpose of researching the Gemological Characteristics and color origin of a new type of jade,which is similar to Dushan jade in Henan Shifosi market.Polarization microscopy,X-ray powder diffraction,Raman spectroscopy,electron probe and infrared spectroscopy have been used.The color span of"Dushan jade"in Philippines is not large,white?green and black are the main colour,brown and cyan-grey is rare,and its color distribution is uneven.Its foundational color is caused by green or black minerals lying on the white base.Green is star-dotted and cluster-like,and black is star-dotted or cluster-like.Glass gloss to grease gloss,translucent-opaque,delicate texture,heterogeneous fracture,sample surface distribution shows unique texture which is similar to the"water line"and transparent veins.Its refractive index is 1.56¹.67,relative density is 2.69².83,and Mohr hardness is 5.21⁶.81."Dushan jade"in Philippines is mainly composed of patchy metamorphic structure,micro-fine-grained metamorphic structure,fine-grained metamorphic structure,granular metamorphic structure,and massive structure.The chemical composition of"Dushan jade"in Philippines is mainly SiO₂,Al₂O₃ and CaO,it also contains Cr₂O₃,FeO,MnO,TiO₂,MgO,etc.The mineral composition includes Anorthite?An96.73 for feldspar?,Diopside,Tremolite,Garnet?mainly Uvarovite and Grossular?,Thomsonite,Chromite,Zoisite,Sphene,Prehnite,Chlorite etc The infrared spectra of"Dushan jade"samples of different colours in the Philippines are very similar,which correspond with the standard infrared spectra of Dushan Jade very well.Among them,the absorption peaks of Garnet are found in the vicinity of843cm^-1,825cm^-1,461cm^-11 and 429cm^-11 for green samples,and the absorption peaks of Tremolite are found in the vicinity of 998 cm^-11 for black-green samples.The main chromogenic minerals of green samples are green Garnet?mainly Uvarovite and Grossular?.There are two strong and wide absorption bands between400-480 nm in blue-violet region and 570-670 nm in yellow-orange region,which are related to the absorption of Fe³⁺and Cr³⁺and are mainly absorbed by Cr³⁺.The chromogenic minerals of blue-gray samples are mainly Diopside,with absorption near 449nm,652nm and 730nm,and mainly caused by Fe³⁺and Cr³⁺and also Fe²⁺.The chromogenic minerals of"Dushan jade"in the Philippines are mainly Tremolite,their absorption are near 548nm,626nm and 727 nm,which are related to Fe³⁺,Cr³⁺and Fe²⁺;the chromogenic minerals of black-green samples are mainly Diopside and Tremolite,their absorption are near 444nm,670nm and 733nm,and are related to the absorption of Fe³⁺,Cr³⁺and Fe²⁺.In brown samples the chromogenic minerals are mainly chromite and sphene.Their absorption bands are between 380-600 and660-730 nm,which are related to the absorption of Fe³⁺,Cr³⁺,Fe²⁺ and Ti⁴⁺.