I have read that visitors to the only active diamond mine in the U. S., in Arkansas, can hunt there for diamonds and keep any they find, regardless of size. (Visitors prospecting for diamonds must pay a nominal fee.)
What I would like to know is: Granted that diamonds as found in the ground certainly don’t look like the ones you see in a jewelry store (facets, glistening, etc.) how does someone hunting for diamonds know one when he finds it?
I’ve been there and it was fun, although I did not find any diamonds.
If I recall correctly, it was a large field that was plowed and there really wasn’t anything there but dirt. So, if anyone found a clear-ish, greasy looking rock of any size, it was probably a diamond.
Again IIRC, I think there was a building there that had examples of rough diamonds, so if anyone needed a visual reference, it was nearby.
The park you are referring to is Crater of the Diamonds State Park in Murfreesboro, Arkansas. I have been there to dig for diamonds so I think I am qualified to answer this question.
The short answer is that it is a state park and it is geared towards education and entertainment rather than profit. They have Park Rangers trained in mineralogy and gemology to help you identify whatever you find as well as help you pick out your prospecting equipment. They are more than happy to look through your collection of funny colored rocks at the end of the day and (probably) tell you why they aren’t diamonds but will still make a good souvenir. However, people do find real diamonds there with some regularity and some of them are quite large including one over 40 carats.
Crater of the Diamonds State Park is Americana at its finest but it isn’t for the faint of heart. The mining field is huge (37 acres) and is constantly plowed so it can be anything from muddy to brutally hot. I made the mistake of going there in mid-August when the dark dirt on the field heated it up to over 120 F. I am from the Deep South myself but it was like Tarzan hot out there. I only lasted a couple of hours before I gave up and decided diamond mining is not for me. The Park Rangers in the air-conditioned visitors center were very nice and helpful though.
Sounds a bit like opal hunting in Spencer, Idaho, just off I-15. Tiny little town in the heart of Opal country. If you go to the cafe there, you can pay a fee and go hunt in the slag pile behind the restaurant. The slag is hauled there from local mines and is replenished from time to time. The folks that own the cafe will show you what raw opal ore looks like (it’s not at all what you might imagine), give you a bucket and a small shovel and turn you loose. Great food there, too.
There’s a similar operation for rubies somewhere in Georgia. It’s a for-profit enterprise, not a park, but the owners realized that while mining probably wouldn’t be profitable in itself, they could still turn a buck off of tourists. Most of the reddish stones found there are garnets, not rubies (and they’ll gladly tell you the difference), but you’ll find a few rubies, and it’s not like garnets are completely valueless, either.
You can prospect for the clear quartz crystals known as “Herkimer diamonds” at the Herkimer Diamond Mines in upstate NY.
You can sift through wet gravel looking for sapphires in Philipsburg, MT. At least there you’re sitting at a park bench outside of a store in town, instead of being out in the middle of a field somewhere. And, yes, there are employees in the store ready to assess what you think you found, and tell you what your tiny little glassy colored rock is worth. So it’s the same business model as the place in Georgia.
Afterwords you can get a malt at a little malt shop down the street. Touristy as all Hell, but a pleasant way to spend a summer afternoon.
Thanks to all. 
I also remember the spot at Knott’s Berry Farm in Buena Park, CA, where park patrons are invited to try their luck at panning for gold at a real gold stream. I tried it myself but didn’t really find anything…
I’m amazed you found funny colored rocks. I’ve been there and I didn’t find a damn thing. I gave up pretty quickly, though. It was hot and I had my dog with me.
For me, this poses a new variant of the Travelling Salesman problem. Let’s say that I want to visit the USA for a two-week period and during that period, I want to spend the a prospecting for the maximum diversity of precious metals and gemstones, spending up to a day each on the actual prospecting activity, what is my route?
I’ve gone to the diamond park several times since high school. It’s a 2 hour drive away. I took my daughters when they were teens. You definitely want to go early Spring or Fall.
It seems to be a matter of luck. Some of the bigger diamonds were found within a short time. People literally walk out there and pick one up
Other people spend days out there sifting dirt. It’s just luck.
I’ve found several small diamond chips. Nothing of great value. Eventually I want to get a ring made for my wife. I still need a few more chips.
I always figured they salted that stream.
I once had a small vial of Knott’s Berry Farm water with a few tiny flakes of gold that I panned as an 11 year old child in the 70s. It would really suck if they lied to me and those flakes weren’t gold.
I thought that was Disney Land. My Father pointed out that the guy helping me swirl the pan around reached into his pocket and put the gold dust into the pan.
You can do that at the Crow Creek Mine outside of Anchorage. It was an active gold mine way back in the day, but is now a tourist attraction. I spent a lot of time up there when I was a kid, as my best friend’s grandfather owned the property.
No, it was Knott’s. I was alone all the time I did it and I watched the guy pour the contents of the pan into the vial. No chance to add anything before he handed it to me.
I remember going to the diamond mine in Arkansas way back in 1963. I don’t recall all that much since I was only 9-10 at the time, but I do recall there was one section with a large machine that was loading up dirt and running it through, presumably sift it for debris that might have diamonds in it.
Don’t know if that was part of the park system or if some company was paying for the rights to do that.
We went to both during the Great American Vacation when I was a kid.
Was it in a tiny screw cap jar with a black lid?
No, it was a slim little glass vial with a white screw-on cap.
Yes, it was at Knotts and of course they salted the stream.
They charged you $x, and you got out 1/3 or less X of gold.
However, I happened to be there with my pan, around 8yo, when the guy salted it, and got a nice amount, which according to my Dad (who panned gold in Alaska) was worth several times what we paid.
Hardly enuf to pay for the trip, of course.
Then mine was Disney, and fake. 