The Jade Belt Slide is the twenty-first treasure that can be found in Uncharted 2: Among Thieves.
The Jade Belt Slide is found in Chapter 4 - The Dig. Located in the cavern where the remains of Marco Polos fleet lie dead. Before you grab the amber 'blue stone' and fashion a torch out if it, you'll first want to search for this item. As soon as you drop down into the cavern Turn to your right and walk along until you see a large statue on the ground. You want to look up and you will see there is another of the same large statue. Look to the right and you will see the glimmer. Use your firearm to shoot the treasure down.