Solution: In Peter's Garden

Answer: ROCK SALT

Written by The Enigmatologists

Start by placing arrows in the grid to form a path that goes through each rock, using the numbers on the right and bottom of the grid to determine how many arrows can be in each row/column.

The rock numbers correspond to rocks in the Peter Russell Rock Garden (as hinted by the title of this puzzle). Use the online map of the garden to determine the name of each rock. You may now notice that the sum of the letters in these rock names equals the length of the path you drew in the grid. Then you can write out the names of the rocks visited in order, along the path, with one letter in each square. The letters in the squares with rocks spell IT IS HALITE. The answer is ROCKSALT (which is another name for halite).

Authors' Notes

In the original version of this puzzle, the final answer was extracted as the first letter of the first rock, the second letter of the second rock, and so on. One of the testers said they had instead tried writing the names of the rocks along the path. We thought that was more fun so made the switch. During the hunt we noticed that this final step wasn't as obvious to all the teams though!