There are indeed parks for rockhounds where you can, if you know what you are doing, find gemstones that you are allowed to keep.If you think it might not be worth the effort, think again. Associated Content reported that earlier this year, eight-year old twin boys found a 2.5 carat rough diamond at the Crater of Diamonds Park in Arkansas, USA ! The Park's February 7 news release reported that Jim Gatliff of Arkansas found a 2.67 carat yellow diamond (picture) in the same park. The Crater of Diamonds Park is the world's only diamond mine open to the public. It's really finders keepers regardless of value. More than 600 diamonds are found there each year. Other gemstones there include amethyst, agate and jasper.
The Eagle Creek Agate and Opal Beds, about 6 km from Burns Lake in the geographic center of British Columbia, Canada is also another site where mineral collecting is allowed. Agate and common opal can be found here. Rare fire opal, too if you are very fortunate.
For the true adventurers, try rock hounding for lapis lazuli in Katannilik Territorial Park , Nunavut, Canada on southern Baffin Island.