A peaceful kingdom ruled by King Fret and Prince Pine, and the setting of Yoshi's Safari.
The kingdom gets its name from the gems that maintain peace and stability across the land. When Bowser and his Koopa Kids stole the gems, a massive earthquake split the island into a light realm and dark realm. Bowser took control of the dark realm, holding Prince Pine in captivity, while his kids ran riot in the light realm with King Fret as their prisoner.
Princess Peach heard about the invasion and asked Mario and Yoshi to help save her friends. They set off, armed with a Super Scope, to take down Bowser's armies and restore peace to Jewelry Land.