How to play

• Every day there's one mystery rock, mineral or gem — the same for everyone.
• You start with a zoomed-in, blurry photo. Each guess zooms out and sharpens it.
• Every wrong guess unlocks a clue: type, color, hardness, structure, then where it's found.
• The table compares your guess with the answer — arrows tell you whether the answer is harder or softer.
• Six guesses. A new rock appears at midnight UTC.