Gemological Characteristics Of Morganite From Brazil

Morganite,also known as pink beryl,is mainly produced from pegmatite and is less well known than emeralds and aquamarines,which are both members of the beryl family.Research on morganite in this area helps to deepen the understanding of the metallogenic environment of morganite and can be used as certain reference for finding new mining areas.This dissertation tests the basic gemological properties of the morganite samples produced in Brazil.Then,we make further analysis of the samples using some large instruments.For example,in order to study the spectral characteristics of Brazilian morganite,we use Fourier transform infrared spectroscopy?IR?,Raman spectroscopy,and ultraviolet-visible light absorption spectroscopy.Electron Microprobe Analysis?EMPA?is also used to test and analyze its chemical composition.We also compare the various characteristics of morganite from other places.Gemological test results show that the color of Brazilian morganite pink,orange pink,orange,and etc.The color saturation is medium to low,and there are also very light and almost colorless morganite.Refractive index is 1.578-1.586,birefringence is0.008,and relative density 2.76-2.80.Non-characteristic absorption spectrum observed under a spectroscope,with obvious dichroism and light orange/orange,light pink/pink.Most samples have weak UV fluorescence,and some samples are inert to ultraviolet fluorescence.The EPMA results show that the content of MnO in Brazilian Morganite is high,with an average of 0.012 wt%;the content of Cs₂O is quite high,with an average of3.589 wt%.Compared with other origins morganite,it is found that Afghanistan and Madagascar have extremely high Cs₂O content,while the United States has lower Cs₂O content.By combining the results of IR and Raman spectroscopy,the characteristics of the molecular vibration mode are analyzed.The results show that the spectrum is basically consistent with the beryl spectrum.The infrared spectrum shows that the structural vibration area is concentrated in the fingerprint area in the range of 400-1200 cm^-1.The results of Raman spectroscopy analysis are 1068 cm^-1 is caused by Si-O non-bridge oxygen in-plane stretching vibration,with 1009 cm^-1 due to Be-O non-bridge oxygen out-of-plane stretching vibration,and 686 cm^-1 due to Si-O-Si deformation internal vibration.The 400 cm^-1 peak is corresponding to the out-of-plane bending vibration of O-Be-O,and 320 cm^-11 being the out-of-plane bending vibration of Al-O.It is found that the level of Cs content will cause a certain degree of displacement of the position of the vibration spectrum peak of the Si-O-Si ring.Through ultraviolet-visible absorption spectrum test,combined with trace element composition,it is obtained that the Brazilian Morganite is caused by Mn²⁺.