The Study On Gemological And Mineralogical Characteristics Of Turquoise Apophyllite From Huanggangliang Deposit In Inner Mongolia

Apophyllite samples were collected from Huanggangliang skarn type rich iron ore deposit in Inner Mongolia.The gemological and mineralogical characteristics of green apophyllite from Huanggangliang in Inner Mongolia were systematically studied by means of conventional gemological characteristic test,X-ray fluorescence spectrum test,Infrared spectrum test,Raman spectrum test and UV-visible spectrum test.Apophyllite is a layered silicate mineral.Most of the crystal are plate prismatic shape.The crystal size is small,self-shape to semi-self-shape.The color of apophyllite is different shades of green,glassy luster,low birefringence,with 2.5 to 5.5 hardness.Under polarized light,interference color is low,gray blue abnormal interference color.The crystal plane stripes and crystal plane steps can be seen after magnification,pitting and white fibrous associated minerals on the surface,and dark columnar solid inclusions in the interior.The dark inclusion is dark cyan under natural light and green under the transmitted light.The main elements of the sample are Si,Ca and K.The content of CaO was higher than the theoretical value,and the presence of SO₂ was detected.The high ignition loss proved that the green apophyllite of Huanggangliang in Inner Mongolia was symbiotic with gypsum minerals.The content of Fe₂O₃ varies greatly,the content of MnO is stable,and the chromogenic element is Fe.The differential thermal analysis spectrum shows three adjacent endothermic valleys and a small exothermic peak.Endothermic valleys at 299?and 351?are caused by dehydroxylation and defluorination;460?endothermic valley is the escape of residual water,OH^-and a small amount of F;330-340?to remove water molecules,release two different states of structured water,and discharge F at the same time;The exothermic peak at 880?is caused by the low temperature?-wollastonite crystallizing into a new phase.According to infrared spectroscopy,1674 cm^-1 is the internal vibration of crystal water,1126,1103 and 1027 cm^-1 is the Si-O stretching vibration.Several absorption bands in the low-frequency region are the bending vibration of Si-O or Si-O-Si,and476 and 415 cm^-1 are the external vibration of crystal water.According to Raman spectral analysis,the characteristic peak of fluorapophyllite was shown in the apophyllite sample.There was only an absorption peak at 3557 cm^-1,which could be distinguished from hydroxyapophyllite.The dark inclusions in the interior show the characteristic Raman spectral peak of the aktinolith,and the white symbiotic minerals on the surface show the characteristic spectral peak of the tremolite,which suggests the apophyllite is symbiotic with the tremolite.The difference between the aktinolith and the tremolite is that the scattering peak around 415 cm^-1,with scattering peak in tremolite sample.By comparing the positions of Raman peaks of aktinolith and tremolite,it can be found that the aktinolith has a more shift toward the low-frequency region than tremolite,which is caused by Fe²⁺replacing Mg²⁺with Fe²⁺.In UV-visible spectrum test,some of the red light is absorbed and reflected in the yellow and green areas,presenting a green tint.