I offered Alexco Resource (AMEX: AXU) as one of my top buy recommendations within the precious-metals patch at the beginning of this year. But so far not even a 29% increase in the price of silver year-to-date, and the company's smooth transition from mine developer to low-cost silver producer, have managed to move the needle on this deeply underappreciated stock.

Following a 125% advance in 2010, as construction of Alexco's Bellekeno mine advanced alongside breathtaking high-grade exploration results, a certain degree of sluggishness might have warranted. But Fools, I believe the stock is now a coiled spring that combines a bargain valuation with enormous long-term growth prospects.

In its first two quarters of silver production, Alexco delivered more than 0.9 million ounces of silver alongside prolific byproduct production of lead and zinc. Those byproducts, coupled with a successful ramp-up process to date, permitted Alexco to realize a 25% cost reduction quarter-over-quarter to just $6.30 per ounce. And that was despite some intermittent power outages in June that hampered mill throughput. The company expects to produce between 2.2 mllion and 2.5 million ounces of silver overall during 2011, but this successful inauguration of Bellekeno operations is only one facet of Alexco's exciting growth story.

The Keno Hill silver district in Canada's Yukon, where Alexco holds the commanding land position, is credited with some 217 million ounces of historical silver production during the 20th century. That prompted silver stream holder Silver Wheaton (NYSE: SLW) to praise Alexco's "immense exploration potential and future production upside" back in 2008. The company has already pinpointed 9.5 million ounces of easily accessible silver in mine tailings from one former mine site and discovered some extremely high-grade silver discoveries at deposits such as Onek, Lucky Queen, and Silver King.

Another alluring deposit located near Alexco's milling complex -- called Flame & Moth -- has already been traced across a 500-meter strike length and 320-meter "down-dip." Importantly, even as recent drill assays from Flame & Moth come back with hits like a 6-meter interval of 31.5 ounces of silver per ton, the deposit remains open in all directions. Fools may recall, from this discussion of Brigus Gold's (AMEX: BRD) 147 Zone discovery, that the phrase "open in all directions" is like music to a resource investor's ears.

And finally, Alexco offers a unique element for investors through the company's environmental-services business. In fact, it was through Alexco's success in landing a long-term mine-site remediation contract the historic mines at Keno Hill that the company acquired rights to explore and mine these properties in the first place.

While the investor's road to silver exposure most commonly leads to world-class deposits in Mexico such as Coeur d'Alene Mines' (NYSE: CDE) Palmarejo mine, or the respective Guanajuato operations of Endeavour Silver (NYSE: EXK) and Great Panther Silver (AMEX: GPL), Alexco's Keno Hill district is undeniably one of the premier silver districts in the world. Particularly given the stock's lack of momentum thus far during a strong year for silver prices, I consider Alexco Resource a world-class choice for silver investors.