The only real "crafting" part here involves making a small container for the candy. If you have access to a craft shop with an aisle of Wilton's products, you can buy small cellophane bags there that would look perfect (though the bags at that link are a bit larger than what I create below). If you don't, or would rather not make the trip or spend the money, here's the frugal version.
Cut a rectangular corner piece from a plastic bag. Fold clear tape over one of the open edges, and add a hunk of rock candy. Then, fold tape over the remaining open side to seal it.
I thought of two ways to use the rock-ness of the candy in the message. I made up the names, and added a bit of a love triangle, for fun (not shown: Mary confessing her devotion to Emma).
First up, a card for miners. Note the semi-on-purpose, child-like scrawl. The pickaxe is made from scraps of brown and silver paper, and the candy bag is simply taped to the back.