Selling numbered rocks, you get whatever's next in sequence

Are the rocks ethically sourced?

Good point.

“All park resources are protected so that all visitors may enjoy them. It is against the law to remove any of the natural (petrified wood, other rocks, plants, animals) or cultural resources (pottery pieces, arrowheads, Route 66 debris), including picking flowers.”

https://www.nps.gov/pefo/faqs.htm

All rocks sourced from private property and licensed commercial operations. No collection from public or protected lands.