The FTSE 100 fell 30.7 points to close at 5,415.60 this afternoon, weighed down by miners after earlier gains in the banking sector.
The index seems to have recovered from yesterday's computer hitch, however.
Kazakhmys shares fell 9.28 per cent to 904.5p, while shares in Eurasian Natural Resources dropped 8.69 per cent to 762p.
Metal prices have fallen sharply in recent weeks, causing a slide in mining stocks.
Stocks in banks and consumer companies were buoyant this afternoon, as the US government takeover of Fannie Mae and Freddie Mac boosted confidence.
Shares in Barclays were up 3.03 per cent to 365.75p, while HSBC was up 1.37 per cent to 906.25p.
Broadcaster ITV benefited from the appointment of a new finance director, as Emap's Ian Griffith's joined the company, and rumours Silvio Berlusconi's Mediaset was mulled a takeover bid. Shares jumped 4.09 per cent on the news.
Anthony Grech, market strategist for IG Index, said: "The banking sector in London has remained strong following the weekend bail out of Fannie Mae and Freddie Mac by the US government and the likes of Barclays and RBS are showing gains on the day in excess of four per cent so far.
"However, mining has one again taken a bath today with significant losses across the sector. With commodity prices continuing to unwind, and with so many constituents on the UK index this could well be the driving force over the weeks to come.
"Although the recent welcome recovery in financials has eased some of the pressure for the FTSE, it is starting to look like there could be another fresh storm brewing that could hinder any progress in the market for the medium term."