The Star of Adam is an oval-shaped blue star sapphire, currently the largest star sapphire in the world. It weighs 1,404.49 carats (280.898 g; 9.9084 oz), and its estimated cost is at least US$ 100 million. However, its expected worth at auction is up to US$ 175 million. Prior to its discovery, the Black Star of Queensland, weighing 733 carats (146.6 g), was the largest star sapphire gem in the world. The blue-colored gemstone has a six-pointed star-shaped reflection or distinctive mark in the center. Later, the gemstone was valued at over $300 million.