Antiques Bottles - can be found deep under original locations of outhouses.  An outhouse is used to be the old toilet and garbage pit.   Use Sanborn maps, to locate outbuildings.  Some public libraries have access to these maps for free.

 

Old Coins - you can find old coins and even cached money in old farm houses, by the old well, old big trees, next to post of fences, ghost towns, in the walls and floors of old houses.  People in the olden days doesn't trust the bank and so they keep and bury their money around their houses.  Most of the times they forgot where it is located and it's left uncovered even after their death. 

 

Diamond - find diamonds at the Crater of Diamond in Arkansas. It's best to go there after the rain because it washes the dirt away and sparkling diamonds appear.

 

Gold - There are so many places to find gold. The best tip is, if a gold was found in a particular place, there will always be gold there even years after years.  You can go to Sonoma, California to find some gold.

 

Gold Coins - thers a lot of Spanish shipwrecks in Florida.  Even at the shores of Vero Beach, Florida you can find valuable coins.  In Key West, Florida you can dive in for gold coins and artifacts worth millions of dollars still uncovered as of to date.

 

Meteorites - using a metal detector, you can find meteorites in Santa Fe, New Mexico;  Brenham, Kansas;  Texas

 

Opal - you can find Opal in Bonanza, Nevada.  Black opal is more expensive. You can find fire opal in Juniper Ridge, Oregon.