Lithium prices are down 40% in a year -- and Albemarle stock is down more than 50%.Albemarle Corporation (ALB -9.18%) stock tumbled 10.2% through 10:20 a.m. ET Friday, and it's not hard to figure out why. Over the last two days, not one, not two, but four separate analysts have lowered price targets on the lithium miner.That's the bad news. The good news is that every single one of these analysts still thinks Albemarle stock is underpriced, and most think the stock remains a buy.What Wall Street says about ...