Thermopolis

Thermopolis, Wyoming is home to Hot Springs State Park, Wyoming's oldest state park (established 1897) and the site of one of the largest mineral hot springs in the world — over 3 million gallons a day of 135°F water flowing across terraces of white, yellow, and brown travertine along the Bighorn River, viewable from a suspension footbridge.[1][2] Our database's coordinate for this entry actually lands just north of Thermopolis town, closest to the Lucerne area right at the park's edge — consistent with the park being the intended location.[3] Travertine here is extensively documented; the second listed specimen, selenite, is not. And regardless of what's technically present, Wyoming state park rules prohibit removing any rock or mineral material without prior permission — so this is a look-don't-take destination.

Hot Springs State Park sits on the north edge of Thermopolis, Hot Springs County, along US-20. The park is easy to reach by paved road and has parking, a bathhouse, and a boardwalk/suspension bridge for viewing the travertine terraces.[1][2]

Not permitted. This is a look, don't take, site — see "Know before you go."

Wyoming State Parks regulations explicitly prohibit removing rock, mineral, or soil material from state park land without prior permission from the superintendent. The exact regulation reads: "the destruction, injury, defacement, removal or disturbance in any manner of any building, sign, equipment, monument, statue, marker or other structure, or of any animal or plant matter and direct or indirect products thereof, including but not limited to petrified wood, flower, cane, or fruit, egg, nest, or nesting site, or of any soil, rock or mineral formation, artifact, relic, historic or prehistoric feature, or of any other public property of any kind on park lands is prohibited without prior permission of the superintendent."[4] Call the park superintendent's office (307-777-6323) if you have a specific reason to request permission; otherwise, come to look, not to collect.