Local collectors and dealers have donated thousands of mineral and fossil specimens, polished stones, gems, crystals and related items for exhibitions, prizes and sales, said Anna Domitrovic, the museum's curator of mineralogy.

"We take at least 200 flats (of boxed stock) up to the sale every year," Domitrovic said.

Hourly silent auctions will provide opportunities to buy stones, fossils, books or posters. Opening bids start as low as $2. For two bits, visitors can spin the "wheel of minerals" to win crystals or polished stones.

Mineral exhibits grouped by locale or species will fill the museum's Ironwood Gallery, where the event attracts "quite a few collectors and dealers" hunting for prized finds, Domitrovic said.

A lapidary will demonstrate the cutting and polishing of stones. Microscopes will reveal micromounts, minerals no larger than grains of sand. Other demonstrators will create artistic bottle stoppers out of minerals and wood and turn silver into jewelry.

Visitors can also stop by the museum's regular exhibits related to the event, including the "fossil dig" in "Ancient Arizona" and the mine dump. Books on related subjects are available in the gift shop.

The show and sale will run from 9 a.m. to 4 p.m. Saturday and 10 a.m. to 3 p.m. Sunday. It's part of the museum's regular admission: $9.95; $1.75 for ages 6 to 12.