44 Martin Pl., SydneyIt isn’t easy to outshine the shimmering blue water of Sydney’s world-famous harbor, but the luxe gems that populate the city’s oldest jewelry store come pretty close. For more than 150 years, discerning Antipodeans have coveted the bespoke creations and world-class service that are the hallmark of Fairfax & Roberts, located in an elegant showroom at the base of the Henry Davis York Building, a 1930s landmark along a bustling pedestrian mall in Sydney’s central business district. But this is no stodgy, white-glove operation: A makeover of the store’s elegant Diamond Room and the recent arrival of sales director and brand-strategy powerhouse Venietta Slama-Powell are a sign this heritage jeweler wants to entice a new generation that will flock to its beautifully presented cases for an eye-catching investment piece. The French RevolutionLast year, Fa