Can you use fossils on Unique items and if so what resonators can be used to do so ?

First question - can you use fossils on Unique items ? I ask because most of the resonators mention modifying an existing rare property or upgrading an item to a rare.

Second question - if the answer is yes - what resonator can you use to do so ?

I know you can use vaal orbs but there is a case I'd like to try with fossils instead. Prefer to know if someone else has done this first before spending my hard earned chaos orbs.

No.

There are two types of resonators. Alchemical Resonators turn a common item rare. Chaotic Resonators reroll a rare item.