The Emerald Chalk Riddle

I slipped through the backdoor screen into the bright noon breeze, chattering non-stop about whether stones prefer shade or sunshine and why gravel crunches under every slide! Right beside a weathered wooden tool caddy rested a thick stick of pale mint-green pavement chalk, rolled right up against a broad, flat slate tile. Could it write a secret riddle without ink? Is it a dry green egg waiting to hatch letters? Cautious, I pressed my snout against the chalk stick, leaning my plush chin in to steer it across the rough slate. Scritch-skrrtch! With a dry, satisfying rasp, the chalk dragged along beneath my heaves, leaving behind a broad, dusty green serpentine squiggle that mirrored my own curves. Chattering rapid theories about what alphabet it might belong to, I looped my body tight along the dusty line, delighted by the powdery green trace left on the slate!