Answer: Doorstop

In 1938, a young Australian boy named Roy Spencer was exploring his father’s prospecting claim in the Anakie Sapphire fields, Australia’s largest sapphire mining area. While poking about, he found an enormous black crystal that he wasted no time in ferrying back to his home to show to his father, pioneering miner Harry Spencer.

His father didn’t contest the unusual size of the crystal, but after examining it, he put it aside. Although it isn’t clear why his father disregarded the stone, it’s possible that he didn’t consider it a viable candidate for cutting as at the time black sapphires were unknown, and the large crystal would just look like a novel crystal formation found within the sapphire mines and hardly more valuable than quartz. The huge crystal was relegated to serving as a doorstop in the Spencer household.

After a decade as a humble doorstop, it came to Spencer’s attention that sapphires could take the form of black gemstones, and he began looking for a buyer for the enormous 1,156 carat stone. In the late 1940s, it was purchased by a jeweler for $18,000 who, after extensively studying the stone, cut it down to 733 carats to reveal a brilliant black star sapphire.

The stone would go on to be known as the Black Star of Queensland and over the ensuing decades would spend time on loan with the Smithsonian’s Natural History Museum, another few decades changing hands through anonymous sales, another period on display at the Royal Ontario Museum of Canada, and is now held in a private collection.