Weight: 5 lb.
Estimated Value: 50,000 gp
The typical crystal ball is about 6 inches in diameter. While touching it, you can cast the scrying spell (save DC 17) with it.
Scrying Spell: Once a day, the crystal ball allows you to see and hear a particular creature you choose that is on the same plane of existence as you. The target must make a wisdom saving throw, which is modified by how well you know the target and the sort of physical connection you have to it. See the complete spell details for more information
Source: DMG p159