We visited the Ace of Diamonds mine over Memorial Day weekend 2014.
The day was partly cloudy - not the best for crystal hunting, but that's the day we had! We left due to 1. Crazy rain/thunderstorm and 2. Fatigue from breaking rocks. :)
The folks @ AoD were super friendly. They have a great shop at the mine where you can rent goggles, hammers, buckets, chisels, screens, etc. Each tool is about $1-2 to rent and you return them at the end of the day.
Be prepared for some hard labor to break the rocks. We did find some small crystals on the ground. But I think the good stuff is still hiding in one of those rocks on the hill!
We'll definitely be heading back to Ace of Diamonds again!