357 Millburn Ave., Millburn, N.J. Behind a quaint storefront on Millburn’s main drag sits Jhanna Fine Jewelry, a haven for suburban New Jersey luxury jewelry lovers Walking into Jhanna Krentsel and Rudolf Shtainhorn’s Jhanna Fine Jewelry store, customers pass between potted flowering vines, under a peace sign fashioned from silvery balls, and into what feels like a carefully coiffed cave, with dark stucco walls that help all that glitters within shine more brightly. There’s a whimsical chair crafted out of cattle horn and hide, an oriental rug, and other seats molded from Indonesian tree roots. Beneath the high pressed-tin ceiling, a large sprig of coppery vine—which Krentsel found while walking to work one day—emphasizes the showroom’s naturalistic bent. Owners and designers Krentsel and Shtainhorn are partners in business and life. After graduating from the Fashion Insti