Study On The Color Of Zhanguohong Agate From Xuanhua,Hebei Province

Zhanguohong agate from Xuanhua,Hebei Province is a kind of cryptocrystalline quartz,which has pure red and yellow colors as well as complicated bands.in this thesis the coloration mechanism of Xuanhua Zhanguohong agate is studied by polarizing microscope,cathodoluminescence,electron microprobe,X-ray diffraction method analysis,laser Raman spectroscopy,UV-VIS spectrophotometer,and differential thermal analysis.Xuanhua Zhanguohong agate is surrounded by trachyandensite and has typical multicolor banded structure and geode.Data of electron probe experiment proves the existence oftrace elements such as sodium,calcium,potassium,iron and manganese in agate.X-ray diffraction experiment and laser Raman spectra proves that chemical composition in Xuanhua Zhanguohong agate,besides containing quartz and oblique silica,hematite and goethite,pyrolusite and manganese minerals In all of the samples,the different structure of the warring states period onyx almost all contain oblique silica,and the content change of inclined silica gradient is bigger,measured in Xuanhua,Hebei Zhanguohong agate lowest inclined silica content in the samples was 16.03%,the highest can reach 81.18%.Result of differential thermal analysis shows that water occupies less than 1%of the agate.Ultraviolet visible dividing meter experimental data show that Xuanhua Zhanguohong agate:absorption is evener,red and yellow have obvious selective absorption to visible light,Black agate on different wavelengths of visible light absorption is relatively uniform.By the above results,the color of Zhanguohong agate is caused by trace elements and point-like inclusions.Quartz with sodium and calcium is white.Agate with hematite is red.Goethite causes yellow color.The co-existence of hematite and geothite produces orange color.Agate with pyrolusite in it is black.Braunite causes brownish black color of agate.The co-existence of pyrolusite,manganite and goethite can produce yellowish brown color.What is more,quantities of quartzs will produce light color while more colored minerals will deepen the color of agate.Xuanhua Zhanguohong agate inclined silica content of itself also has a certain relationship:the high degree of bright red xuanhua the warring states period of onyx its oblique silica content is relatively high,color slants deep brown-black xuanhua Zhanguohong agate the silica content is higher.A thin belt xuanhua white near the center of the agate warring states onyx its oblique silica content is higher than near the edge of agate white wide stripe.Blue,purple,pink,xuanhua Zhanguohong agate is moderate to high content of silica.And the high degree of bright yellow xuanhua Zhanguohong agate is not always higher than the oblique silica content,cannot prove color more bright-coloured inclined silica content is higher.Zhanguohong agate from Xuanhua,Hebei Province is formed in medium and low temperature hydrothermal conditions.According to the geological background,iron and manganese may come from local iron and manganese deposits.It is the hydrothermal fluid with abundant Si O₂ that carrys them to agate deposits.Goethite and manganite can precipitate and crystallize from the liquid.The formation of hematite may result from goethite dehydrated reconstruction as the temperature of hydrothermal liquid increases in later stage.Andpyrolusite can be formed by manganite's dehydration and oxidation.