摘要:
应用中国地质大学(武汉)珠宝学院自制的激光诱导离解光谱(LIBS)设备对5块已知成分和32块未知成分的翡翠进行测量,采用优化外标法分析了LIBS测试稳定性与测量精度,测试计算结果平均值与真值偏差小于1%,测试计算结果标准偏差优于1.2%;通过测试结果计算待测样品的晶体化学通式,其不同晶位阳离子系数总数之比为(0.913~1.075)∶(0.902~1.182)∶(1.909~2.087),基本上符合翡翠阳离子晶位系数1∶1∶2的理论值,验证了LIBS定量区分硬玉与绿辉石的可行性。试验样品的LIBS定量分析结果显示,硬玉与绿辉石中SiO2的质量分数基本上稳定在59%左右,硬玉中Na2O和Al2O3的质量分数分别在13%和23%左右,CaO,FeOT,MgO的总质量分数低于4%,而绿辉石中Na2O和Al2O3的质量分数比硬玉的低,翡翠中CaO,FeOT,MgO的总质量分数随着绿辉石的质量分数增加而增大,可达到27%。此外,绿辉石中Na2O和CaO的质量分数呈现很好的负线性相关,相关系数r1=-0.990 1;Al2O3与MgO的质量分数也呈现很好的负线性相关,相关系数r2=-0.966 6。
Abstract:
Five jadeite samples whose components are known and thirty two samples whose components are unknown were measured by Laser-induced Breakdown Spectrometer(LIBS) developed by Gemmological Institute of China University of Geosciences(Wuhan).The authors adopted optimized external standard method to analyze the testing stability and measurement accuracy of LIBS.The test average was less than 1% deviation from the true value,and the test standard deviation was better than 1.2%.The chemical formula of the sample is easily calculated with the help of test results.The ratio of the sum of different crystal cations coefficient is(0.913 to 1.075) ∶(0.902 to 1.182) ∶(1.909 to 2.087),which is basically in line with the theoretical value of jadeite cations crystallographic sites coefficient 1∶1∶2.The result verified the feasibility of using LIBS to distinguish jadeite from omphacite.The LIBS result of quantitative analysis of the test sample shows that the contents of SiO2 in jadeite and omphacite are usually stable at around 59%,the contents of Na2O and Al2O3 in jadeite are about 13% and 23% respectively,and the total contents of CaO,FeOT,and MgO is less than 4%.However,the contents of Na2O and Al2O3 in omphacite is less than that in jadeite.In jadeite,the contents of CaO,FeOT and MgO increases as omphacite increases and it could reach to 27%.In addition,the contents of Na2O and CaO in omphacite shows negative linear correlation,the correlation coefficient r1 =-0.990 1,and the contents of Al2O3 and MgO shows negative linear correlation,the correlation coefficient r2 =-0.966 6.
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