The S&P 500 Index (^GSPC -0.16%) set a new all-time closing record for the third time this week on Friday. Behind the advance was the Labor Department's monthly nonfarm payrolls report, which showed a stronger jobs market than Wall Street expected. The S&P is now up 2% in 2014, and 24% in the last year; the benchmark index added one point, or 0.1%, ending at 1,878 on Friday.

 Coal miner Peabody Energy (BTU) was the index's most severe decliner, dropping 5.3% in trade on Friday. The losses follow a sudden shift in the structure of the business, as well as an executive shakeup, both announced on Wednesday. Peabody Energy, like other coal miners, has been hit by reports that Chinese banks may be increasingly reluctant to loan to real estate developers. China's real estate boom has driven demand for steel -- which is partially composed of coal -- and due to this dynamic, high rises in China have quite a bit of relevance to American portfolios with exposure to coal companies. Thankfully, Peabody is also involved in the thermal coal business, helping it to diversify. 

Shares of another materials company, Freeport-McMoRan Copper & Gold (FCX 0.41%), shed 4.9% Friday after a power-rationing plan in the Congo raised fears that the company's operations could be adversely affected. The Congo is in a bit of an energy crisis, and lacks the resources to supply both its populus and the mining interests in its nation with adequate energy. The Congo situation aside, copper prices plummeted 4.2% today, and the price of gold also fell, naturally putting a strain on Freeport-McMoRan Copper & Gold's profitability. 

Finally, shares of (CRM 1.35%) lost 3.8% today, as fallout from the company's statement earlier in the week intensified. On Tuesday, disclosed that it couldn't differentiate between money it pulled in from new customers, and money it received from existing customers upgrading. Consider the fact that the stock is fairly volatile, and technology was already one of the worst-performing sectors of the day, and today's slump starts to make some sense.