UPDATE 1-Striking S.Africa gold miners reject pay rise offer

* Union says options now exhausted

* Platinum output falls 1.9 pct in August

(Adds details and background)

JOHANNESBURG, Oct 11 (Reuters) - Striking South African gold miners have rejected the industry's latest wage offer, the National Union of Mineworkers (NUM) said on Thursday, dimming hopes that wildcat strikes that have paralysed the industry could come to an end.

"This was a final offer from the companies. They said take it or leave it," NUM spokesman Lesiba Seshoka said. "Now that it has been rejected our options have been exhausted."

Since August almost 100,000 workers across South Africa - including 75,000 in the mining sector - have downed tools in often illegal and violent strikes that may hit economic growth this year and undermine investor confidence in the minerals hub.

Africa's top two bullion producers AngloGold Ashanti

and Gold Fields have been hit by an estimated 48,000 miners taking to the streets fighting for higher wages.

The wildcat strikes, which started in the platinum industry and spread to other mining companies and beyond, have raised questions about President Jacob Zuma's leadership and tarnished South Africa's reputation among foreign investors.

Production of platinum group metals fell 1.9 percent in August compared to the same month last year, data showed on Thursday, a sign the unrest was taking its toll on Africa's biggest economy.

Gold output still rose 0.4 percent in August as the strikes only spread to bullion the following month.

The rand fell to a 3-1/2 year low against the dollar earlier this week and Moody's cut South Africa's government bond rating last month, citing the government's difficulty in keeping up with spreading unrest.

(Reporting by Sherilee Lakmidas, Agnieszka Flak and Tiisetso Motsoeneng; editing by David Dolan)

((agnieszka.flak@thomsonreuters.com)(+27 11 775 3154)(Reuters Messaging: agnieszka.flak.thomsonreuters.com@reuters.net))