Investing in gold and silver miners paid off this month for investors in equity exchange-traded funds.

BlackRock Inc.’s iShares MSCI Global Gold Miners ETF, known as RING, has returned almost 14% in August, more than any other unleveraged stock fund in the U.S., data compiled by Bloomberg show. Close behind, with gains approaching 13%, are two funds of silver miners, with strategies tracking ore extractors accounting for eight of the top 10 performers.

With bond yields increasingly depressed, many investors that are taking off risk are heading into alternatives, like commodities. Just this week, gold prices rose to a six-year high and silver touched its strongest in two years, as concerns the U.S.-China trade war is weighing on global economic growth boosted the appeal of havens. Gold rallied nearly 7% in August, and silver climbed 13%.

“Gold’s current price level hints at a potentially longer, sustained rally,” according to Joe Foster, a portfolio manager and strategist at VanEck. “We believe this, along with the steps gold miners have taken to reduce costs and capital expenditures, make gold stocks an attractive opportunity,” he wrote in an emailed note this week.

This story was provided by Bloomberg News.