A few mineral collection things that I do all the time:
Take a boat from Meadow to Big Forest Isle. When you get there, go directly west. You'll run into a few things on the way, such as a log or a couple trees, but if you try to keep on that path you'll come up to a huge group of rocks to mine. Scarf those babies up and sell them!
OR
Go to Dry Isle, then Desert Isle. If you have 1000 Dollars, take the donkey. But if you don't then just follow the south most beach until you find the row boat. Take that boat for a 100 dollars over to Sheer Isle. Once there, follow the rocks until you find the cave inside. Don't worry about getting lost, the caves aren't that windy. The crystals there can provide some really good stones, sell those and you can get about 50,000 Dollars if I do so remember.