I voted for the third option. It usually goes like this at my table:
DM: "You find three gems."
Bob: "Do they look valuable?"
DM: "Make an Intelligence (Nature) check."
Bob: (rolls) "Ugh, five."
DM: "You can't tell for sure, they might be valuable, or they might be cut glass."
Joe: "Can I try?"
DM: "Maybe. What are you going to do differently?"
Joe: "Um...I'm proficient with gemcutting tools, I know a little more about gems than Bob does."
DM: "Sure, roll a Intelligence (Gemcutting) check."
Player: (rolls) "Sixteen?"
DM: "These are definitely valuable. One is an onyx worth 50gp, and the other two are opals worth 75gp each."