I always thought it was eye black...never thought about it being the turf. I have a 17 year who likes to slide so I gave up at least 4 years ago. This weekend he one-upped stains and slid holes into a pair of pants, a sock, his hip and his outer knee (two different slides). Socks (for one slide) and pants for the other were both black so I consider it a solid win even if he's in pain. LOL