An example of a unique jewel with a radius is the one I'm currently using called overwhelming odds which gives defense buffs to my main attack cleave. In order for a unique jewel to take effect though, you will need a certain amount of either strength, intelligence, or dexterity passive nodes around the jewel. Overwhelming odds, for example, has a requirement of 40 strength of nodes around the jewel. Bear in mind you won't actually see the radius of the jewel until you equip it!