Miners remain under a cloud as metal prices retreat.Mining giants BHP Billiton and Rio Tinto have confirmed that their proposed $116bn Pilbara iron ore joint venture is dead in the water.The companies had agreed in December of last year to establish a production joint venture covering the entirety of both companies' Western Australian iron ore assets, but the hook-up has run into regulatory opposition, prompting the companies to abandon the idea.Other miners are also in the doldrums as metal prices sag. The nine biggest fallers among Footsie constituents are all miners. A note from HSBC suggesting that investors should switch from stocks with exposure to copper to those in the aluminium sector has put a dent in the share prices of Antofagasta, Vedanta and Xstrata . HSBC rates both Antofagasta and Xstrata as "sells" and no longer rates Vedanta as worth buying.With gold and silver both weaker there is no enthusiasm for precious metals miners Randgold and Fresnillo either.GB Group is among the risers in a buoyant software sector. The identity management company thinks full-year profits will beat expectations after a strong first half during which revenue jumped 10% to £11.5m and underlying profit more than doubled to £740,000.Top performing sectors so far todayHealth Care Equipment & Services 3,136.14 +2.42%Technology Hardware & Equipment 599.11 +2.29%Software & Computer Services 675.45 +2.11%Financial Services 5,673.50 +1.88%Fixed Line Telecommunications 2,028.29 +1.63%Bottom performing sectors so far todayIndustrial Metals & Mining 7,217.22 -1.35%Automobiles & Parts 4,096.29 -1.30%Mining 24,486.81 -1.15%Real Estate Investment Trusts 1,973.62 -0.68%Aerospace and Defence 3,435.74 -0.28%