Disscusion On Genesis Of Zhanguohong Agates From Xuanhua,Hebei Province

Zhanguohong agate from Xuanhua output in basalt.Zhanguohong agates has been microscopically observed and analyzed about structural causes summarizing the results of previous studies.Main experiments include observation under microscope,SEM,CL,BSE,electron microprobe analysis,XRD and TGA.The influences of quality appraisal of Zhanguohong agate is also discussed as well as the identification from other deposits.Raw materials of Zhanguohong agate from Xuanhua are mostly spherical or nearly spherical,clear concentric ring band,with red and yellow stripes commonly seen.They can be seen in two main forms under microscope: macrocrystalline quartz of different sizes;radial distribution of chalcedony which showed in tiny grains,short fibers,long fibrers.Agate bands periodically repeated,and tiny grain-short fiber-long fiber intermittently appear,indicating during the crystallization of agate,environment has changed,resulting in non-uniformity of the internal structure,appearation and disappearation of fiber morphology.Tiny globulites are commonly seen on the surface,which continue to accumulate to develop to sheet structures;structural differences between the strips are clearly remarkable: light-colored bands mainly showed layer and sheet structure with small ball crystal grains and small holes.,while the darker bands showed long flake parallel with irregular edges.Plate-edge like structure displays in thr fracture,as well as a large number of holes and a film bending.Diamond fracture of trigonal mineral has been proved to be the results of calcite,spectrum analysis of test results in this area a lot of calcite,which was detected by spectrum analysis.CL?BSE and electron probe synthesis proved that,calcite emits orange-red light under CL,some iron mineral cause dark-colored strip emit orange-red light,while light-colored strip does not emit light.Main minerals of Zhanguo-hong agate from Xuanhua are quartz,secondary minerals are moganite and goethite.TGA experiment approved that the major impurity is water,total content of which is 0.9%.In this paper,three typical structures are described and discussed,which are angular rhythmic structure,"?" character-shaped structure,and quartz-filled structure respectively.The centers of eyelike Zhanguohong agate are usually made of calcite,quartz,or several iron-bearing minerals.They can form the same band structure agate,can also be mixed to form crystal nucleus.Zhanguohong agate is affected by different temperatures and pressures.The iron minerals are separated from the agate particles.They grow into branches along the fibrous structure of agate.It Makes that very similar to the shape of the grass in the macro.