March was the cruellest month for BlackRock World Mining Trust as its investments in mineral stocks took a bath.The group reported a 7.6% fall in net asset value (NAV) in March, although the end-March figure still stands 4.3% higher than the end-2011 figure.Furthermore, the performance in March bested that of the HSBC Global Mining Index, the index against which the trust benchmarks its own performance; the index was down 10.2% in March and was only up 0.8% on the year at the end of March.Over the past year the NAV is down 16.4%, but up 41.4% over the past five years. It is only over the five-year interval that the trust fails to beat its benchmark index, which rose 46.6% over the five years to the end of March 2012.The trust's largest holding is Rio Tinto at 9.3% of the portfolio, followed by BHP Billiton at 8.1%. Gross assets at March 31st were £1,391.6m, with short term borrowings £42.56m. Gearing stood at 3.2% and the share price discount to the NAV was 11.6%. The share price fell 0.67% to 665.50p by 14:11. NR