Answer: Flint fracture surface
by MarbleGhost · 192 guesses · hard
What you're looking at
Flint is a hard, dense sedimentary rock made from microscopic quartz crystals. You'd normally spot it as dark grey or black pebbles in riverbeds, on beaches, or embedded in chalk deposits. It's famous for its use in prehistoric tools and historic fire-starting mechanisms.
When you zoom in extremely close on a flint fracture surface, you're looking at the conchoidal fracture pattern, a smooth, rippling texture created when the stone breaks. This close-up view strips away the context that makes flint recognisable, revealing only curved ridges and glassy planes that could belong to almost any smooth, brittle material.
Search for smooth, rippling concentric patterns and glassy surfaces typical of stones that fracture in predictable ways.
How players did
86 players made 192 guesses. It took 191 guesses before someone got it right.
Most common wrong guesses: gold leaf, satellite image, stone, slate, charcoal
