shares of rio tinto plc rio inched down 031 to £5212 friday on what proved to be an allaround grim trading session for the stock market with the ftse 100 index ukx falling 008 to 743457 rio tinto plc closed £1194 short of its 52week high £6406 which the company reached on january 26 trading volume 12 m remained 20 million below its 50day average volume of 32 m editors note this story was autogenerated by automated insights an automation technology provider using data from dow jones and factset see our market data terms of use