Mineralogical Characteristics Of The Chambersite In Jixian,Tianjin,China

Chambersite is a rare manganese borate mineral with formula:Mn₃B₇O₁₃Cl.It was first discovered at Barber's Hill salt dome,Chambers County,Texas,USA.The mineral is also known from the Dongshuichang deposits in Jixian,Tianjin,China.Dongshuichang deposit is the only commercially valuable Chambersite deposit in the world.Chambersite in this deposit is fine and usually occurs as aggregate as spherical or sunflower shape.Because of the size of the mineral,there is several reports about the mineralogical characteristics of Chambersite.This paper studied the mineralogical,chemical composition and crystal structure of Chambersite.1.Aggregates of Chambersite are spherical shape.Particles of Chambersite is light gray,its size is fine,about 30-100?m.The gangue minerals are typically composed of micritic quartz,dolomite,pyrite,etc.2.EPMA analysis was used to test the chemical composition of Chambersite,and calculated the average formula is:(Mn_2.05,Fe_0.05)B_7.61O₁₃Cl_0.84.The value of Boron isotope of Chambersite is between 7.79‰and 11.90‰,it indicates that the origin of Chambersite is marine evaporate.The cell parameters is a₀=0.865638±0.0001nm,b₀=0.866915±0.0004nm,c₀=1.223638±0.0003nm,Z=4.In-situ and ex-situ diffraction patterns were observed at different temperatures,and the phase transition of Chambersite is between 403?and 411?.3.In this paper Raman spectroscopy and Infrared spectroscopy were used to study the molecular vibration of Chambersite.The characteristics of Raman spectra have been discussed,and the preliminary band assignments have been proposed.Raman bands at 1468,1303cm^-1 are assigned to the non-symmetric vibration of[BO₃].Raman bands at 1231,1189,1116cm^-1 are attributed to the B-O in-plane bending modes.Raman bands at 920,836cm^-11 are symmetric vibration of[BO₃].The bands at662cm^-1 together with bands at 600,404 cm^-1 are assigned to the trigonal and tetrahedral borate bending modes.The intense infrared bands at 1402,345cm^-1;153,1052,984cm^-1;944,920,899,869cm^-1;847,820,770,702cm^-1;685cm^-1 are assigned to the non-symmetric vibration of[BO₃],the Mn-Cl in-plane bending modes,symmetric vibration of[BO₃],symmetric vibration of[BO₄],and trigonal and tetrahedral borate bending modes,respectively.4.Compared with Chambers County,Chambersite in Jixian has quite different characteristics like the fine grain size,irregular crystal shape,smaller cell parameters and d-values,and weaker Raman bands.