I just saw the show on diamond mining in Arkansas. It was very interesting! I would like to build a small wooden box screen as used on the show. What size should the openings in the screen be? Thank you.

You can find the heavy wire screen at your local hardware or garden supply store, they usually sell it as garden fence to keep critters out of your garden. It's usually sold in rolls and is made with different size openings such as 1/4", 1/2" etc. - hope that helps!

It really depends on the size of the crystal or rock which you think you will find. At the Oceanview Mine in Pala, CA, they supply each screening station with two screens. You stack the 1/2 inch screen on top of the 1/4 inch screen and dump the bucket of dirt over the top.
Then you rinse what is left in the 1/2 inch screen in the water first. Hopefully it has some bigger chunks of smoky quartz or aquamarine. After that, you rinse the 1/4 inch screen and look for the smaller crystals like the tourmaline.

At home, I use a finer screen, which was actually sold as a desk inbox at Target. It catches the tourmalines which are the thickness of pencil lead, which would usually slip through the 1/4 screen when it is agitated in the water. ellen

Like Ellen mentioned, 1/2". 1/4", and a 10 or 20 mesh screens work well.