Polymetal shares plunged almost nine per cen after HSBC cut the stock from overweight to neutral, although it did raise its target price from 730p to 820p. Hochschild Mining was also heading south after Goldman Sachs reiterated its sell rating on the group. Meanwhile, Centamin and African Barrick Gold were both on the rise, boosted in part by a higher gold price and perhaps also by reports that they both last week outperformed the price of gold, which rose 1.5% to $1,399 an ounce. FTSE 250 - RisersCentamin (DI) (CEY) 41.20p +3.65%Premier Oil (PMO) 355.10p +3.20%Ocado Group (OCDO) 298.90p +2.71%African Barrick Gold (ABG) 169.80p +2.04%Cairn Energy (CNE) 277.80p +1.83%NMC Health (NMC) 336.50p +1.66%UBM (UBM) 713.00p +1.64%Perform Group (PER) 510.00p +1.29%Big Yellow Group (BYG) 412.70p +1.23%Cranswick (CWK) 1,144.00p +1.15%FTSE 250 - FallersPolymetal International (POLY) 738.00p -8.83%Thomas Cook Group (TCG) 136.50p -8.20%JPMorgan Indian Inv Trust (JII) 286.00p -6.90%Hochschild Mining (HOC) 224.10p -6.59%Imagination Technologies Group (IMG) 262.40p -5.81%Jupiter Fund Management (JUP) 340.10p -5.00%Pace (PIC) 276.70p -4.72%Bank of Georgia Holdings (BGEO) 1,710.00p -4.42%International Personal Finance (IPF) 583.50p -4.42%CSR (CSR) 497.70p -4.20%NR