Mineral collecting Puns

I'm working in a chemical plant / mining plant this summer, and was on the phone with my grandma discussing my job:

Me: "the plant also has a mining operation"

Grandma: "oh you're not going to be a miner are you?!?"

I hear my Grandpa in the background: "well he's not 21 yet Patti."

He immediately started laughing and drew a collective ugh from my grandma and I.