MP Materials said on Wednesday it would sell $500 million of its common stock, a day after the U.S. rare earths miner inked a supply deal with Apple. Shares of MP Materials fell 5.8% in extended trade.

MP Materials launched a $500M public offering of common stock, and expects to grant a 30-day underwriters option to purchase up to an additional 15% of shares to be sold in the offering.

Shares of MP Materials were up 26% in midday trading at $61.19, putting the stock on pace for a record closing high. Apple stock was up 0.6%, while the S&P 500 was flat and the Dow Jones Industrial Average was down 0.6%.