Mineralogical Identification and Genesis of Celadonite in Green Moss Agate from Fuxin, Liaoning, China

The mineralogical characteristics and formation mechanism of the green phase within moss agate remain debated. With large quantities of green mineral inclusions, the moss agate from Fuxin (China) provides an excellent natural laboratory for resolving these issues. This study presents petrographic, spectroscopic, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA) data to determine the composition and texture of these green inclusions. The agate predominantly occurs in pores and fractures of andesitic breccias of the Lower Cretaceous Yixian Formation. Microscopic observations reveal various morphologies (filamentous, clustered, platy, globular, and irregular) and tones (light, dark, true, and yellowish green) of the inclusions. X-ray diffraction (XRD), infrared, Raman spectroscopic, and EPMA analyses demonstrate that the inclusions are rich in celadonite. Compositional or color zones are observed for both celadonite-rich regions and the agate. SEM imaging reveals euhedral celadonite crystals increase progressively in size across older-to-younger growth domains of each zone. The euhedral habits of celadonite, the systematic grain-size increase in celadonite-rich zones, and the zoned structure of the agate collectively suggest that the agate and celadonite within it precipitated from hydrothermal fluids.