High Desert holds a 70 per cent interest in the Gold Springs gold project on the border between Utah and Nevada.
South American Silver said it bought the shares for investment purposes.
Under the deal, South American Silver paid 18 cents per share for 15.58 million shares of High Desert.
The shares are subject to a four-month restricted resale period that expires April 29. Meanwhile, South American Silver has been granted the right to maintain its interest in High Desert at 19.9 per cent for 36 months should the company issue additional shares.
South American Silver is developing the Escalones copper-gold project in Chile and the Malku Khota project in Bolivia.
South American Silver shares were down three cents at 25 cents on the Toronto Stock Exchange, while High Desert shares were up two cents at 14.5 cents on the TSX Venture Exchange.