Glencore increases Century Aluminum stake slightly - filing

(Adds details on share conversion, price performance)

NEW YORK, Jan 5 (Reuters) - Glencore PLC (Xetra: A1JAGV - news) converted some of its preferred shares in mid-sized U.S (Other OTC: UBGXF - news) . aluminum producer Century Aluminum Co (NasdaqGS: CENX - news) into common stock worth about $200,000 at the end of 2015, boosting its stake slightly, a filing showed on Tuesday.

The Swiss trader and miner, which was already Century's largest shareholder, converted 456.38 convertible preferred shares into just over 45,000 common shares, taking its overall stake to 37.35 million common shares.

The raises its stake to about 42.97 percent, up slightly from 42.91 percent.

Century's shares have plunged by about 85 percent, to around $4.30, over the past year as a global aluminum surplus and concerns about slowing economic growth in China, the world's top producer and consumer, have curtailed metal prices.

Aluminum prices have lost about a quarter of their value since May last year and were around $1,460 per tonne on Tuesday.

(Reporting by Josephine Mason and Luc Cohen; Editing by Bernard Orr and Dan Grebler)