At the top of this forum is the "Trade Skill Sticky" which has a link to the mining guide on this site:
Trade Skill Sticky Allakhazam Mining Guide This should help you:
Quote:
Silver - Alterac Mountains, Arathi Highlands, Ashenvale, Badlands, Darkshore, Desolace, Duskwood, Dustwallow Marsh, Feralas, Hillsbrad Foothills, Loch Modan, Redridge Mountains, Searing Gorge, Silverpine Forest, Stonetalon Mountains, Stranglethorn Vale, Swamp of Sorrows, Tanaris, The Barrens, The Hinterlands, Thousand Needles, Westfall, and Wetlands
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Silver is a rare spawn of Tin; find tin nodes and eventually they respawn as silver. You can level up to Iron level (125) solely on tin; it is just a little slower