During the day you pay $100 for a whole day of digging which allows you to fill a 5-gallon bucket. At night the cost jumps to $500, but can be split between two people. One person wears the lamp and both people look. You can rent the black light for $100. Gum found her stone worth more than the cost of the dig at night. The total value of the gems she found was $2,040.

What you pair digging with: You can camp at the mine or at a campgrounds near by. The area of the Coast Mountains and the San Joaquin Valley is stunning and there are remnants of the area's mining history. The mine's Web site suggests riding OHVs, motorcycles or dune buggies to the mine since the road is rugged. Don't bring the family car unless it's hearty is the basic idea behind the suggestion.

Digging drawbacks: You can dig all day without much success of finding benitoite, although, the thrill of the possibility can keep one looking. At night, the word cold doesn't even capture it. Gum said it was 15 degrees.

Family Plus: This is something the whole family can do and kids under 14 are free. Camping at the mine is only $20 per night per family. Even if you don't find benitoite, you'll find other minerals. Kids like rocks.

There's more: Head to W. Scott Forrest Gemstones in Clovis, CA to get the benitoite appraised and then to Leher Design in Larkspur, CA to turn it into jewelery.