Look for pebbles by the roadside, in beds of streams and riverbanks.
Go out into the country for ledges on hillsides. Every road cut,
cliff, bank, excavation, or quarry shows rocks and minerals.
Railroad cuts, rock pits, dump piles around mines, building
sites--they'll all yield specimens. Some of the best mineral
specimens collected in New York City came from skyscraper and subway
excavations. Help a New England farmer clear his field and you'll
have more rocks than you know what to do with.
As for reference books, many states publish guides to mineral
deposits. Mineralogical magazines list mineral localities.