Microstructure Of Albite Jade From Myanmar And Its Gemological Signiifcance

Petrologically the albite jade is chiefly composed of monomineral albite existingas associated mineral for the jadeite jade of the jadeite ore deposit in the Myanmar.The exploration scale of jade similar to jadeite is becoming more and more larger forlack of the sufficient jadeite resource reserves during which people gradually paymore attention on albite jade. Thus the price of the albite jade is higher year by year.Minerallogically the albite jade belongs to the end member of plagioclase and alkalifeldspar, whose microstructure and rheology features conspicuously play a vital partin understanding the plastic deformation process of the feldspar.The study of microstructure and rheology of the albite jade known as associatedmineral for the jadeite could reveal the stress, strain, the relation of temperature andtime of the albite jade consequently making it possible to recognize the geneticdistinction between the jadeite and the albite jade. Nearly icy albite jade known as thesimilar jade of jadeite is considered as the ideal sample for studying the plasticdeformation of the feldspar, whose textural and microstructural characteristicscontribute to understanding how jade quality and gemological features get affected bythe jade textures.Based on the sample features, the representative ones are selected to conduct thedetailed observation and classification of the texture and microstructure of the albitejade using the optical microscope. Depending on the grain size, metacryst texture canbe subdivided into medium-grained metacryst texture, fine-grained metacryst texture,tiny-grained metacryst texture; Depending on the grain unconformity degree,metacryst texture can be subdivided into equigranular metacryst texture, porphyriticmetacryst texture, inequigranular metacryst texture;Depending on the grain inclusion relation, metacryst texture can be subdividedinto inclusive metacryst texture, embedded metacryst texture, helicitic metacrysttexture. Thus microstructural features are characterized by wavy extinction,deformation pattern, deformation twin, sub-grain, core-mantle structure, deformation zone and so on. Microstructural mechanism includes microscopic rupture, dislocationglide, dislocation creep, swelling recrystallization, sub-grain rotation recrystallization,grain boundary migration recrystallization and a new type recrystallization caused bydeformation twin, in which this term is proposed for the first time in my study.Besides, the deformation recrystallization temperature estimated depending onthe deformation features of the feldspar enables us to conduct the preliminary study ofthe deformation influence factors and rheology implication. All these abundantinformation about the textures and microstructures above serves as a significantapproach to study the microstructure mechanism of the albite jade and its gemologicalmeaning.By way of the scanning electron microscope, the further study of the microscopicrupture of nearly icy albite jade reveals the mechanism of the microscopic rupture.The testing results show that the interface, micro-fissure, cleavage surface, twincomposition plane and holes of the crystal grain exist ubiquitously in the albite jade,which will strongly affect the jade quality and the other gemological characteristics ofthe albite jade. The data of the EBSD for the sample shows that there exists thepreferred orientation in the albite aggregate,which therefore makes it possible for usto study how the external conditions such as temperature, the deformation mechanismof dynamic recrystallization and the textural features of the grain size and boundaryaffects the preferred orientation of the albite jade.