The Logan Sapphire weighs 423 carats and is the heaviest mounted gem in the National Gem Collection. It was mined in Sri Lanka and donated to the National Museum of Natural History in 1960 by Mrs. John A. Logan.

One person had asked if these gems are replicas. They aren’t – they’re the real thing, part of the museum’s priceless gem collection. Some people may remember a gem exhibit I photographed at the Hillwood Estate, jewels previously owned by heiress Marjorie Merriweather Post. She had donated many of her pieces to the Smithsonian, and this is where they’re normally displayed.

Chalk Emerald, posted earlier: