Minera Frisco SAB is the region’s best-performing mining stock this month and has returned 93 percent this year. Not a single equity analyst recommends buying the shares.

Frisco, the gold and silver producer owned by billionaire Carlos Slim, is having its best year since beginning trading on the Mexican Stock Exchange in 2011, buoyed in part by investors turning to precious metals amid market instability spurred by the U.K.’s secession from the European Union. This month, Frisco’s returns of 28 percent are outpacing international competitors such as Barrick Gold Corp., China’s Zinjin Mining Co. and Mexico silver giant Industrias Penoles Sab, according to data compiled by Bloomberg.

Analysts aren’t convinced. Morgan Stanley and Credit Suisse Group AG recommend selling Frisco shares, while Moody’s Corp., citing "pressure in the company’s credit metrics from deteriorating market conditions, and the low likelihood that cash flows and credit metrics will improve" in the short-term, downgraded the company’s rating to B3 in April.

"I would think some of the share increases we have seen in the mining sector are slowing," Bernardo Trejo, a mining equity analyst at Invex Casa de Bolsa SA in Mexico City, said in a phone interview. "Companies heavy in gold and silver have benefited from the international rally we’ve seen in the markets."

Frisco, whose shares fell 62 percent last year, accumulated $1.39 billion in debt as of the first quarter while gold production dipped 12 percent compared to a year earlier. Frisco faces a "refinancing risk" given its high debt levels and "it is uncertain whether the company will be able to cover its upcoming debt commitments with internal cash generation," according to Moody’s.

Gold futures fell to a three-week low on Wednesday as gains in equities and a stronger dollar curbed demand for the metal as a store of value. Silver extended its longest run of losses in eight months, and shares of miners slid the most since November.

"We are seeing more exposure to risk appetite in the last few days in the international markets," said Trejo. "That could have an inverse correlation for mining companies, which were seen largely as the safe bet during a time of instability and uncertainty."