岫岩玉的穆斯堡尔谱学研究

MOSSBAUER STUDY OF XIUYAN JADE

岫岩玉是我国的主要玉种之一,属于蛇纹石玉。在X射线衍射、红外光谱、可见光吸收谱,及电子显微镜等项研究确切查明主体矿物为叶蛇纹石的基础上,选两个优质玉样进行^(57)Fe穆斯堡尔谱学研究。岫岩玉的穆斯堡尔谱由两组四级双峰构成,第一组双峰(δ=1.12,△=2.73与2.72mm/s)系由镁氧八面体中的Fe^(2+)形成,另组双峰(δ=0.35与0.36,△=0.63与0.55mm/s)反映的是镁氧八面体中的Fe^(3+),Fe^(3+)/Fe^(2+)分别为0.90与0.78。铁是参与叶蛇纹石晶格的组分;Fe^(3+)与Fe^(2+)均处镁氧八面体中;Fe^(3+)/Fe^(2+)近于与小于1是制约它呈绿色的主要因素。

Xiuyan jade,named from Xiuyan county,Liaoning province,becomes one of the major jades in China. Xiuyan jade is serpentine jade in mineralogy, X-ray, infrared spectra and electron microscopic analysis indicates that it consists mainly of antigorite(m{Mg_(31-1/m))[Si_2O_5](OH)_(1+3(1-2/m))}),with minor amount of chrysotile. Choosing two finest jade samples for ^(57)Fe Mossbauer spectra,we have obtained the data of Xiuyan jade as follows:The A doublet is caused by Fe^(2+) in the Mg—O octahedra (δ=1. 12, △=2. 73 and 2. 72mm/s,A/∑A=0. 53 and 0. 57), Whereas the B doublet reflects Fe^(3+) in the Mg—O octahedra (δ=0. 36 and 0. 35,△=0. 63 and 0. 55,Γ=0. 55 and 0. 60mm/s). Fe^(3+)/ Fe^(2+)=0. 90 and 0. 78. The spectra indicates that: (1) Iron in the minerals enters the lattice instead of existing as impurities; (2) Fe^(3+) and Fe^(2+) exist as isomorphism with Mg in the cordinate octahedra; (3) colour of the jade may be resulted from Fe^(2+) vs Fe^(3+) electron transfer in the octahedra,therefore,Fe^(3+)/Fe^(2+) border on or less than 1 is favorite for jade's colour.