There occur two types of rock crystals in Emeishan basalt from Meigu county, Sichuan province: amethyst and the "trichroic"rock crystal of the first oreforming stage in vesicles of basalt and the light color rock crystal of the second oreforming stage in interlayergliding(faulted) fissures or vugs of basalt. The iron oxides in rock crystals are specularite, hematite and lepidocrocite. There are two iron oxides of two types of shape textures: The one is threecircle layered structure peloids occurring within partings(0.4~0.7㎜) of red—brown interstitial layers of “trichroic”rock crystals ,with the diameter of 0.15~0.5㎜, consisted of the spherulite, coccosphere and the surface, the spherulite and the surface are red—brown, but the coccosphere is ferriblack, so called "maily red with black". Scanning electron microscope(SEM) and energy dispersive spectrometer(EDS) analysis indicated that the coccosphere is consisted of the sheet specularite arranged radially around the nucleus. The surface is red semitransparent scalelike。the form of circular spheres or epitaxial growth circular prisms. The other is the twocircle layered structure centralcavity tube, was crystallized in bandings of banded rock crystals of the first generation of the second oreforming stage. The direction of the macroaxis of the tube is vertical to the direction of the simpleform crystal face of rhombohedron of the crystal. SEM and EDS analysis indicated that the center of the tube is hollow. The endocircle is ferriblack sheet specularite. The direction of the sheet is vertical to the macro axis of the tube. The exocircle is differentthikness red—brown hematite. The tube is driplike, stalactitic and inversion calabashlike. Both threecircle layered structure peloids and the twocircle layered structure centralcavity tube were formed on the condition of the strongly acidic and highly oxygen fugacity environment. By using the analysis of the homogenization temperature of the fluid inclusion and Raman spectrum of the crystals, the rock crystals were formed on the condition of epithermal(150°~190℃) ore deposit genesis. The salinity of the oreforming fluid is lower. 5.7%~13.2% NaCl_eq. The salinity of amethyst is highest(13.2% NaCl_eq). The salinity of banded rock crystals is lower(6% NaCl_eq). The fluid inclusion is consisted mainly of H₂O, SO₂and a small amount of CH₄. This study has important significance to understand the growth mechanism, the growth rate, the variation of therrmodynamics under the given condition in ferrous oxide and the differentiation of mineralization stage. It also provides a useful guide to studying the species and mineralization of ferrous oxide under the supergene oxidation condition.