Mining stocks were among the best performers of the day on Monday as gains across the wider sector outweighed heavy losses by heavyweight metals producer BHP Billiton.BHP Billiton was trading 4.1% lower after its South32 spin-off was valued at the lower end of market expectations on its debut on the Australian Stock Exchange.South32, which comprises BHP's non-core assets in aluminium, alumina, manginess, nickel, silver and coal, started trading with a market cap of around $9bn, short of the $10bn-13bn value that some analysts had predicted.BHP is by far the largest company in the UK mining index, though decent gains from the likes of Fresnillo, Glencore, Randgold and Rio Tinto managed to offset its falls.Upbeat comments from UBS also helped shares in the precious metals sector in particular as the bank said gold equities were well placed to offer "genuine leverage to a gold-price recovery"."After significant cost cutting and re-shaping of their business the gold sector is in much better shape than it was at the height of the bull market three years ago," UBS said.The bank reiterated its 'buy' recommendations on Acacia Mining and Randgold and said it sees long-term value potential at Fresnillo. Fresnillo was also rising after saying at its AGM that it remains on track to hit its output guidance in 2015 after a strong start to the year.Elsewhere, Rio Tinto was making headlines on rumours it could raise $1bn from the sale of some aluminium assets. Top performing sectors so far todaySoftware & Computer Services 1,539.79 +2.24%Industrial Metals & Mining 1,939.21 +1.65%Industrial Transportation 3,049.37 +1.55%Oil Equipment, Services & Distribution 18,949.97 +1.20%Mining 14,536.02 +1.09%Bottom performing sectors so far todayFood & Drug Retailers 3,134.72 -0.83%Chemicals 11,820.08 -0.44%Oil & Gas Producers 7,282.23 -0.40%Fixed Line Telecommunications 5,262.84 -0.31%Mobile Telecommunications 5,327.51 -0.31%