The country's top-10 valued firms added over Rs 41,000 crore to their market capitalization during the month ended July 31,with state-run Oil and Natural Gas Corporation (ONGC) contributing most to the kitty. PSU major ONGC added Rs 23,934 crore to its valuation taking its total market cap to Rs 2,49,071 crore at the end of trade in the just ended month. The top-10 coveted club,which comprises six public and four private sector firms,together added Rs 41,131 crore during the month,taking their total valuation to Rs 16,27,549 crore for the month ended July. The total market cap of these top gainers stood at Rs 15,86,418.25 crore on July 1. The country's most valued firm,Reliance Industries saw erosion of Rs 15,768 crore in its market cap in the last one month,after which it stood at Rs 3,08,022 crore. Two PSUs NTPC added Rs 16,491 crore to its market cap while MMTC lost Rs 12,167 crore from their valuation. At the end of the month,market cap of NTPC stood at Rs 1,77,772 crore and MMTC at Rs 1,48,877 crore. Private telecom services provider Bharti Airtel lost Rs 315 crore from its market cap,while National Mining Development Corporation (NMDC) added Rs 159 crore to its market valuation.