Three new sinks promise to enliven the powder room or master bath. Cut from a single piece of amethyst, the Polyedro sink ($50,000) is the functional artwork of Jake Levy, of International Stone Collections, and Franke Kitchen Systems. Levy chiseled a 500-pound stone until he was left with the sink’s 80-pound base, and he placed the amethyst’s purple crystals around the washbasin. The New York–based designer Clodagh has created a distinctive floor-standing sink (starting at $11,995) carved from stone; the desi…