When I had a key to the old Mercantile Library on 47th St, I used to wander through the diamond district every day before sitting down to write. I ate lunch in the upstairs canteens where the traders and cutters ordered food. Eventually I started interviewing people, showing up to events in the Diamond Trader’s Club, visiting cutting rooms, jewelers, scrap dealers, elite traders in colored diamonds. When The New Yorker’s Jeremy Keehn asked me to write about the Lesedi la Rona, the world’s largest diamond, I found that Ronnie VanderLinden, a stalwart of the district who I knew pretty well, a classic old school cutter and trader, had been brought in to assess it. Just a bit of the material I gathered, but a good story: