July 14 (Reuters) - The board of Cornerstone Capital Resources Inc on Tuesday rejected BHP-backed SolGold Plc's takeover offer for the second time, saying it undervalued the Canadian copper and gold miner.

"For the second time, the Board is unanimous that SolGold's proposal substantially undervalues Cornerstone," Chairman Greg Chamandy, who has a 10% stake in the company, said in a statement.

About 65% of Cornerstone shareholders have said they will not support SolGold's second offer. The board also urged shareholders in its statement to reject the offer.

SolGold, the copper-gold company focused on Ecuador, made an all-stock transaction offer of 11 SolGold ordinary shares for each Cornerstone share late in June after its earlier proposal in February 2019 was rejected on grounds that it undervalued the Canadian company. (Reporting by Kanishka Singh in Bengaluru; Editing by Subhranshu Sahu)