A gallery of gems opens May 3 in Los Angeles

Sunset, May, 1985

What destines one mineral specimen for a velvet pedestal while another ends up on the slag heap? You can learn the geological answers in the new "Gemstones and Their Origins" hall, opening May 3 at the Natural History Museum of Los Angeles County. The 2,000-square-foot hall is the world's first museum gallery devoted to the show-and-tell of gem formation, mining, and cutting. Opening-month events make May a good time to visit.

Cases illustrate eight of the world's major gem-generating locales. Exhibits explain gem types, including those formed in mineral deposits concentrated by water (Australia's opals), in molten rock (Brazil's aquamarine), in laval (Thailand's rubies), in explosive volcanic deposits (Africa's diamonds), formed by high pressure (Burma's jadeite), and by high heat (Kenya's garnets).

Photo murals of mining scenes backdrop tools and such touchable specimens as a turquoise boulder and a huge hunk of apple green and lavender jade--the hall's most valuable specimen. For most gemstones, you'll find natural crystals and cut jewels side by side. Look through a microscrope at gem inclusions (flaws the distinguish real from synthetic stones); the images appear on a video monitor.

From May 3 through 5, jeweler Harry Winston will stage his largest-ever Western showing, with gem cutters working in the museum foyer. From April 16 through May, the museum will display a spectacular collection on loan from the Smithsonian Institution, including a 127-carat diamond, Marie Antoniette's diamond earrings, and the 182-carat Star of Bombay sapphire (Actress Mary Pickford used to play catch with it).

The museum is at 900 Exposition Boulevard in Exposition Park, Los Angeles. Hours are 10 5 Tuesdays through Sundays. Admission fee is $1.50 for adults, 75 cents for ages 5 through 17 and seniors.