When source materials are less than precious, the value of jewelry is in its design. There’s a mint’s worth of ideas at Avant Garde, a small boutique on a little-trafficked section of Melrose Avenue west of Fairfax. Behind the bare-bones retail portion of the shop is an atelier where jewelry is made. Designers plate brass (which approximates the look of antique gold) or silver onto a pewter base. The shop’s name is misleading; the merchandise is more crowd pleasing than envelope pushing. Long chains dangling a key or a feather reflect prevailing trends, while earrings that resemble 19th-century French coins point to the Gallic origin of the store’s married designer-owners Marie-Eve and Ami Partouche. Two specialties are cuff bracelets made of colored stones (light and dark pinks in a variety of sizes, for instance) and hammered circles in organic asymmetrical shapes that are linked into bracelets, necklaces, and belts. Chunky pieces grab your attention, but there are plenty of quieter items, such as a silver band featuring a small square of metal for a gem or a weathered-looking silver necklace reminiscent of a pearl choker.