Tomorrow's heirlooms: pendants of plastic fabric stretched over bronze with acrylic lacquer; a brooch of aluminum siding; miniature brass castings of automobile parts; anodized titanium pins in pastel violets with a touch of Plexiglas, Formica, porcelain or rubber for evening wear.

"Good as Gold, Alternative Materials in American Jewelry," at the Renwick through March 28, grants costume jewelry new status as art.

To cash in on the Renwick's theme and the holiday season, four other galleries and shops around town showcase new age ornaments.

Combining fashion, art and design skills, the 92 artists at the Renwick create wearable collages that are sometimes elegant (Eric Hilton's "Winged Heart Pendant" for Steuben Glass), sometimes whimsical (Candace Loheed's ceramic "Ganders" neckpiece). Certain of the 180 pieces are best seen in a museum's glass case. Marjorie Schick's winged armlet "could only be worn to a party," drily notes Renwick Director Lloyd Herman, curator of the exhibit. "You couldn't put a coat on over it."

Japanese metalworking techniques are explored in brooches by Gene and Hiroko Sato Pijanowski and others. Found objects are assembled in several works, including Susan Lowry's spunky "Dog Tags" necklace. Ruth Nivola's "The Ritual Choker" neckpiece looks like something out of Tut's tomb, woven from metallic yarns with silk and brocade fabrics.

Works by 20 of the artists are on sale in the Renwick shop -- from $2 rings made of electrical wiring and plastic to a $300 "pea- picking necklace." Slide-lectures by artists in the show are scheduled for Saturday and Sunday, 10 to 5, in the gallery's Grand Salon.

Plum Gallery (3762 Howard Avenue, Kensington) picks up the theme with "All That Glitters is Not Gold," a well-displayed collection of finely crafted jewelry by 10 artists also in the Renwick show. It's at the Plum through January 5. David Tisdale's anodized metal works include an elegant necklace that juxtaposes aluminum and diamonds. Bruce Metcalf's pins, one titled "Strange Drifting Object No. 1," are drawings laminated between Plexiglas sheets. Mary Lee Hu's necklace of fine silver threads is the most expensive piece in the show at $2500; prices range downward to about $50. Do they sell? Plum's Paula Locker says 17 pieces were snapped up at the opening.

Another 13 artists from the Renwick show have pieces on sale at Smull's (1606 20th Street NW), in "Beyond Gold, New Jewelry: Alternative Materials" through January. Titanium earrings go for $16; the range is up to a few hundred dollars. Brass, paper, Plexiglas, bone, color Xerox, photography, rubber, cloth, wood and ceramic materials are among the alternatives to gold. Thomas Mann's computer-part sculptural pins and Julie Shaw's Lucite and metal items straddle the line between punk and high-style fashions.

"A Touch of Gold: 11 American Art Jewelers," at the Barbara Fiedler Gallery (1621 21st Street NW) has another six from the Renwick show, through December 22. Best- known is high-fashion designer Ivy Ross, whose use of titanium, tantalum and niobium puts her on the scientific end of the jewelry-making scene.

Full Circle Gallery (317 Cameron Street, Alexandria) features three artists in the Renwick exhibit. Susan Tamulevich paints deceptively heavy-looking copper beads with molten 14-karat gold. Helen Banes surrounds an antique Moroccan pendant with new gem stones. Diane Flyr's porcelain geisha girl pins sell for $16.

Additional "non-precious" works by some artists in the "Good as Gold" show and others are on view at Fendrick Gallery (3059 M Street NW), Jackie Chalkley (3301 New Mexico Avenue NW) and Gadfly (215 South Union Street, Alexandria) on a continuing basis.