Size and Rarity
Large sapphires are hard to come by; large star sapphires are nearly impossible to find. While sapphires are mainly graded on color and clarity of the stone, star sapphires are assessed on their presence of asterism, or star quality. The largest star blue sapphire, until now, has been The Star of Adam. At 1404 carats, this stone was mined in Sri Lanka and fetched hundreds of millions when sold. Another notable large sapphire from Sri Lanka is The Belle of Asia, which lacks star quality but boasts 392 carats and sold for $17.3 million at auction in Geneva in 2014.
Sri Lankan star sapphires are a natural phenomenon steeped in value. Because the star quality of sapphires often dissipates in large stones, The Stone of Great Faith, at 2570 carats, is particularly rare.