Transformation Of Micro-crystal Muscovite At Elevated Temperatures

In order to provide the scientific basis for further researching and developing of the new style nonmetallic mineral resources, micro-crystal muscovite, in west Sichuan, China, X-ray powder diffraction and Infrared Spectroscopic(the frequency range 370-4000cm^-1) analysis are used to monitor their characters of mineralogy& petrology and mineral transformation at elevated temperature. Our results suggeet that:There is a mineral association, micro-crystal muscovite and phengite, in this deposit. The mineral combination is that micro-crystal muscovite is about 80% and phengite is about 20%. Their crystallinity is very high and their polytype is 2M₁. Both of them are dioctahedron because the d₍₀₆₀₎ and b of micro-crystal muscovite and phengite are 0.1502nm, 0.9012nm and 0.1505 nm, 0.9030nm respectively ;and the band at 530 cm^-1 splits into bands : 525 cm^-1 and 475 cm^-1. For their d₍₀₆₀₎ and bo are larger than common muscovite and the bonds 525 cm^-1 is smaller than common muscovite, the reason of high content of Fe²⁺ + Fe³⁺and Mg²⁺ in the ore is that Al³⁺ in octahedral are replaced by Fe²⁺ + Fe³⁺ and Mg²⁺, and this is a phengite series mineral association formed through isomorphism replacement.There is a important characteristic that three peaks occurs in thermal-analysis curves. They are 772℃, 929℃ and 1107℃, the pake at 772℃ may be attributed to mineral association: micro-crystal muscovite and phengite. Tranformations of micro-crystal muscovite is mainly a three-stage process in the temperature range 400-1300. First statge: the layer of micro-crystal muscovite is made up Si —O tetrahedron and Al^VI—O octahedron. Second stage: layered structure still maintains, but Al^VI — O octahedron changed into Al^V — O polyhedron. Third stage: micro-crystal muscovite decomposes into 5 — Al₂O₃ and non- crystal compounds of Si-O.