Answer: Serpentinite rock surface

What you're looking at

Serpentinite is a metamorphic rock formed deep underground through the alteration of olivine-rich minerals by water and heat. You'd find it in mountain ranges, quarries, and coastal cliffs around the world. It's sometimes used as a building material and ornamental stone, though certain types containing asbestos fibres are hazardous.

When you zoom in on serpentinite's surface, you see a complex pattern of wavy lines, smooth curves, and subtle colour variations ranging from pale grey to deep green. The extreme close-up hides the rock's overall shape and size, making it nearly impossible to recognise. The texture looks almost organic, like a living creature's skin, which is exactly why identifying this puzzle stumped 62 people before the solution.

Watch for smooth, wavy patterns with flowing lines that suggest a metamorphic texture rather than crystalline or grainy surfaces.

How players did

45 players made 62 guesses. It took 61 guesses before someone got it right.

Most common wrong guesses: dried acrylic, door mat, embossed wallpaper, tile