What is "snakestone"

Snakestone \Snake"stone`\, n.

1. A kind of hone slate or whetstone obtained in Scotland.

2. (Paleon.) An ammonite; -- so called from its form, which resembles that of a coiled snake.

"fossil ammonite," 1660s, from snake (n.) + stone (n.). So-called from the old popular notion that they were coiled snakes petrified.

n. 1 A kind of hone slate or whetstone obtained in Scotland. 2 (context paleontology English) An ammonite (because of its coiled form).