NEW YORK ( TheStreet) -- Solitario Exploration & Royalty ( XPL), Westmoreland Coal ( WLB) and Tanzanian Royalty Exploration ( TRE) were the top gainers last week; North American Palladium ( PAL), Mag Silver ( MVG ) and US Gold ( UXG) lapsed into red territory.Solitario Exploration & Royalty emerged a top gainer last week, rising 20%. Westmoreland Coal followed, gaining 9.7% after reporting first quarter 2011 earnings. The company's operating income for the first quarter stood at $7.4 million as compared to $5.3 million in the same quarter of the prior year. While EBITDA was up 9.7% to $23.3 million, revenue increased by 1% to $127.8 million for the same period. Tanzanian Royalty Exploration, a mineral resource company with exploration-stage properties in gold and silver, rose 5.2% at close last week. Geier International Strategies Fund, a Florida-based investment fund, increased its stake in TRE from 8.77% to 10.3% last week, through the purchase of extra shares in the open market. This buying indicates confidence in the company's Buckreef gold mine redevelopment project for commercial gold production in Tanzania. Carpenter Technology ( CRS) gained 2.8%. Last week, TheStreet upgraded the stock to buy from an earlier hold rating, as it believes that Carpenter Technology had significant net operating cash flows and impressive net income in the recent reporting quarter. Steel Dynamics ( STLD) added 2.8%. Last week, the NYSE Arca Steel index slipped 4.3%. Aluminum prices slumped 0.8% to $2,590 per metric tonne last week. However, aluminum stocks, Alumina ( AWC) and Kaiser Aluminum ( KALU) were up 2.6% and 1.5%, respectively. Zacks Investment Research recently reaffirmed its neutral rating on Alumina. North American Palladium was at the helm of losers, tumbling 29.5% after reporting disappointing first quarter 2011 results. For the quarter, net loss was $10.7 million. Meanwhile, for full year 2011, the company cut down its production forecast to 145,000 to 155,000 ounces of palladium from the earlier guidance of 165,000 to 175,000 ounces. In addition, it raised its cash costs per ounce outlook to $450 from the earlier range of $340 to $370 per ounce. With silver prices dropping 6.5% to $35.4 per ounce, silver stocks erased significant value. Mag Silver eroded 13%, while Silver Standard Resources ( SSRI) and Silver Wheaton ( SLW) declined 6.4% and 4.8%, respectively. Additionally, gold prices lost 1.2% last week and settled at $1,495.02 per ounce. Due to this effect, US Gold declined 11.1%. Others like Coeur d'Alene Mines ( CDE) Stillwater Mining ( SWC), Harmony Gold Mining ( HMY), Golden Star Resources ( GSS) and Eldorado Gold ( EGO) closed 8.8%, 7.4%, 5.6%, 5.4% and 5.3% lower, respectively.