Shares of Fortescue Metals Group Limited (ASX: FMG) have enjoyed a remarkable run over the last month or so. Since hitting a low of just $1.44 on 21 January, the shares have risen more than 45% to $2.09, putting them near their highest price since November.

The sharp rally has largely come about due to the rebounding iron ore price, which has surged from a six-year low around US$38 a tonne late last year to US$51.64 a tonne overnight, according to data from The Metal Bulletin.

This rally has also helped spur demand for shares of other miners as well, including BHP Billiton Limited (ASX: BHP) and Rio Tinto Limited (ASX: RIO), with investors growing increasingly confident that the commodity may have finally found a floor. Indeed, it’s also likely that investors were impressed by Fortescue’s latest earnings results, which it released to the market yesterday.

One of the biggest concerns surrounding Fortescue’s shares in recent years has been its enormous debt pile, which would become increasingly difficult to repay as the iron ore price falls. Thanks to some excellent cost cutting initiatives however, Fortescue managed to repay more than US$1.1 billion in debt during the period. It’s still in a huge net debt position of US$6.13 billion, but it’s gradually cutting that down and thus, reducing the risks surrounding the business.

Meanwhile, it also reported a breakeven price of just US$28.80 a tonne, making it one of the lowest cost producers in the world. That’s certainly a feat you want to have in this low price environment.

Now, I’ll admit that I’ve been surprised by Fortescue’s ability to cut costs and improve its corporate position, and management get a huge amount of credit for implementing those initiatives. What I am concerned about, however, is that the iron ore rebound mightn’t be sustainable.

The fact is, the world’s biggest producers are still producing a record amount of product for a market which, at the same time, is experiencing slowing demand growth. Although prices have risen recently, that isn’t guaranteed to continue and if prices do fall again, it’s likely that investors will sell the miners just as quickly as they bought.

Indeed, Fortescue is doing a great job at the minute, but investors need to ask themselves whether they think the current iron ore price can be sustained. If they think otherwise, they may want to think twice before buying shares of Fortescue.

Discover the 'new breed' of blue chips that could take your portfolio higher in 2016

Forget BHP and Fortescue! These 3 "new breed" top blue chips for 2016 pay fully franked dividends and offer the very real prospect of significant capital appreciation. Click here to learn more.

The report is free! No credit card required.

OUR #1 DIVIDEND PICK FOR 2016...

Forget BHP and Woolworths. This "dirt cheap" company is growing like gangbusters, and trading on a 5.6% dividend yield, FULLY FRANKED (8% gross). With interest rates set to stay at these low levels for years to come, for hungry investors, including SMSFs, this ASX company could be the "holy grail" of dividend plays for 2016.

Enter your email below to discover the name, code and a full investment analysis in our brand-new FREE report, “The Motley Fool’s Top Dividend Stock for 2016.”

By clicking this button, you agree to our Terms of Service and Privacy Policy. We will use your email address only to keep you informed about updates to our website and about other products and services we think might interest you. You can unsubscribe from Take Stock at anytime. Please refer to our https://www.fool.com.au/financial-services-guide">Financial Services Guide (FSG) for more information.

Motley Fool contributor Ryan Newman has no position in any stocks mentioned. Unless otherwise noted, the author does not have a position in any stocks mentioned by the author in the comments below. You can follow Ryan on Twitter @ASXvalueinvest.

The Motley Fool Australia has no position in any of the stocks mentioned. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy. This article contains general investment advice only (under AFSL 400691). Authorised by Bruce Jackson.