BREWER – Rocks in their many guises, be it rough stones, gemstones, geodes, crystals, fossils or slabs, will be the matrix of the Penobscot Mineral and Lapidary Club’s second annual Rock and Gem Show 10 a.m.-5 p.m. Saturday and Sunday, Nov. 4-5, at the Brewer Auditorium.

More than 20 club members will be on hand to show off their collections and the jewelry they have created from stones and gems.

Jewelry maker and metalsmith Donna Tumosa, founder of the club in 2004, said she decided to organize the group because of a “lack of rock clubs in the area.” The club offers field trips to mines in Maine.

“Interest is high in rocks and minerals,” she said. “It’s amazing the beauty that comes from the earth, amazing that the earth creates things like that.” She said she has collected rocks since she was a child and old enough “to get out and play in the dirt.”

Donna Fransen of Hampden joined the club only a few months ago.

“I have always loved rocks and I like looking for them,” she said. She enjoys landscaping her home with rocks she has collected. Club members, she said, are very knowledgeable. “They know where to find minerals and rocks and how to identify them.”

Club trip organizer Brett Leighton of Millinocket has guided rock hounds on expeditions to an amethyst mine in Stowe, to a tourmaline mine in Georgetown, and to the Willis Quarry in Topsham. He is the owner of Katahdin Rock and Gem, a shop that deals in stones.

“There are 1,200 old mines in Maine,” he said. “These were mainly silver, copper and gold mines where you find pegmatite, which yielded feldspar and mica, and where gemstones were found, too. Feldspar and mica mining was viable in Maine until about the 1950s.” Leighton has been interested in rocks for more than 40 years.

“You’re treasure hunting,” he said, “which is part of the appeal. The neat thing about it is that it’s not about money or buying something. You’re going out and digging.”

The three gemstones most people hope to find, he said, are aquamarine, tourmaline – the Maine state stone and the national stone – and amethyst.

At the show, club president Lance Shope of Brewer will give a demonstration on how to cut and polish a cabochon-shaped stone. He will use a rock saw to cut the rock, and other tools to form it into a polished gemstone.

A treasure hunt for amethyst, Maine tourmaline and possibly Western gems and minerals will be available to children at the show for an additional cost of $5 per child.

A silent auction featuring minerals, rock specimens and other rock-related items donated by club members will be conducted. Auction items will include agates, tourmaline, quartz and other kinds of crystals, and other Maine minerals and rocks.

Door prizes will be awarded every hour, and a piece of jewelry made by Donna Tumosa will be raffled at the event.

Last year, Tumosa said, 700 people attended the show. Admission is $1, free to children under 12 accompanied by an adult.

The club, which has 120 members, meets at 2 p.m. the second Saturday of each month at LadySmith Studio and Gallery, 19 Bomarc Road, Bangor. For information about the club, call Tumosa at 947-6200.