Collections

[Yin]

I'm thinking about starting a coin or rock collection. Which one would be the cheapest and have the most benefits in the long run? I love the way rocks look and I already have a few, a chunk of amethyst that I got from the museum and a few polished (I hate them when they are polished I like them straight from the source, dirt and all) common looking rocks. My mom has a bunch of coins from way back when I don't even think I was born yet. And if I decide coins is the way to go, I can just add on to her collection. Soooo..... Yeah. Help me decide.

Also, do any of you have any collections? If so do you have pictures to show your progress? Do you think collections can ever be finished?