Cliffs Natural Resources Inc. (NYSE: CLF) has seen solid insider buying, and the chief executive continued the buying spree. Lourenco Goncalves bought a block of 216,700 shares at prices ranging from $5.00 to $5.20. The total purchase came to $1.1 million. Cliffs Natural Resources is a mining and natural resources company that produces iron ore and metallurgical coal, and it has struggled mightily over the past few years. This may be a very good sign for investors. Shares ended trading on Friday at $5.31, so a good buy indeed.