What: Gold prices continued their nearly four-year slide, down to $1,087 per ounce at 3:30 pm today. The decline in gold prices sent many gold miners reeling, with some of the smaller players, such as Yamana Gold (NYSE:AUY) IAMGOLD Corporation (NYSE:IAG)Silver Standard Resources (NASDAQ:SSRI), and New Gold (NYSEMKT:NGD) declining 10% or more at the time of this writing. 

So what: For a lot of miners, seeing the price of gold fall below $1,100 an ounce is a pretty precarious because very few companies can cover their all-in sustaining costs at that level. One of the reasons IAMGOLDs shares declined more than many others in the space today was that it announced that its projected sustaining costs for gold in 2016 will be in the range of $1,000 to $1,100 per ounce. This situation puts the company either already running at a loss at today's prices or just barely eking out a profit.

Silver Standard Resources also reported its production outlook for 2016 today, and while it didn't give the company's sustaining costs for its gold production, it did estimate its cash costs at $715 to $765 per ounce. Once you add in the company's non-cash costs and capital obligations, it, too, will probably struggle with such low gold prices. 

Neither Yamana Gold nor New Gold reported any major news, but estimates from the company's previous reports suggests that today's prices aren't exactly great news, either. According to New Gold, a gold price of $1,100 per ounce translates to an internal rate of return of a paltry 2.5%, and that was the low end of the company's guidance from its most recent investor presentation.

Yamana Gold's cash costs for 2016 are projected to be $662 per ounce, so it appears that it has a bit more wiggle room to generate a profit from today's gold prices than the other three here. However, Yamana's sustaining and expansionary capital expenditures of $395 million might be a little too ambitious for a commodity that appears to be oversupplied.

Now what: Gold is quite possibly one of the hardest of the commodity markets to understand. Gold's role as a hedge against inflation means that much of the precious metal's price is based on investor sentiment and less on the supply-demand curve. This situation is what makes investing in gold so challenging: There are so many factors that go into the price of gold that it can be hard to predict. One factor that continues to weigh on gold is the strength of the dollar. As long as the dollar remains strong, chances are we won't see much recovery in the price of gold soon. 

For IAMGOLD, Yamana, Silver Standard, and New Gold, cheap commodity prices will lead to weak earnings, but it appears that all of their sustaining costs are low enough that prices at this level aren't the end of the world. If gold continues to slide, though, they may need to reconsider their production guidance or cut some of their capital expenditures until we start to see some recovery in the price of gold.