Study on Material Composition and Origin of Luodian Nephrite With"Pocking Mark"and"Grass Flower"in Guizhou Province
The composition and origin of"pocking mark"and"grass flower"in Guizhou Luodian tremolite jade(Luodian nephrite)were studied using scanning electron microscopy,electron probe,and laser Raman spectroscopy.The test results show that large clumps of"pocking mark"are found at some of the junctions between calcite and tremolite or the crystal boundary of tremolite,and some small pores of calcite or tremolite are distributed with a small flake"pocking mark".Scanning electron microscopy(SEM)and electron probe(EPM)analysis showed that the"pocking mark"was composed of iron oxide,and the Raman spectral peak of the"pocking mark"was hematite.The"grass flower"is the globular or amorphous shape of the"desert rose"and exists at the junction of the two structural tremolites or the edge of the columnar and lamellar tremolites.The"grass flower"in Luodian nephrite was identified as manganese oxide by SEM energy spectrum and EPM surface scanning,and the characteristic peaks of Raman spectra showed that it was calcium manganese(640,356 and 287 cm-1)or hydrohydroxyl manganese(636,582 and 506 cm-1).According to the composition and structural characteristics of Luodian nephrite with"pocking mark"and"grass flower"patterns,it can be inferred that the large clumps of"pocking mark"in Luodian nephrite are caused by the mixing of Fe-rich hydrothermal and tremolite ore-forming hydrothermal.In contrast,the small flake"pocking mark"is formed by Fe-rich hydrothermal filling.The disseminated lamellate or columnar tremolite around the"grass flower"was formed by the mixed crystallization of Mn-rich hydrothermal solution and tremolite jade ore-forming hydrothermal solution.In the later stage,the Mn-rich hydrothermal fluid migrated to the edges or cracks of the columnar or lamellate tremolite and precipitated to form calcimanganite or birnessite.
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