a piece of such rock, which can be used as a magnet and which was formerly used as a primitive compass (原被用作原始指南针，现可被用作磁铁的)天然磁石
a piece of such rock, which can be used as a magnet and which was formerly used as a primitive compass (原被用作原始指南针，现可被用作磁铁的)天然磁石