Cov iav fiber ntau tau yug hauv xyoo 1930s.Nws yog ib hom inorganic non-metallic khoom tsim los ntawm pyrophyllite, quartz xuab zeb, limestone, dolomite, calcite, brucite, boric acid, soda tshauv thiab lwm yam tshuaj raw khoom.Nws muaj lub teeb yuag, siab zog, siab thiab tsis kub tsis kam, corrosio ...
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