Coal miner's discovery (4)

I believe the answer is:

seam

(Other definitions for seam that I've seen before include "Sewing join" , "A stitched join in a garment" , "Join in knitted garment" , "Sewn join" , "Stratum (of a mineral)" .)

I've seen this clue in The New York Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.