摘要
When we investigated the occurring conditions of the iron-riih deposits in Jining-Erlian area, Nei Mongol, in 1977, many opaque and shiny steel balls about 200μ in diameter have been found in the strong magnetic fraction of both natural and artifact heavy minerals from the Wenduermiao Group and Bainaimao Group. Examinations of different approaches led to the conclusion that they are the cosmic dusts.
