Black Sand Basin, Geothermal basin with hot springs in Upper Geyser Basin, Yellowstone National Park, United States.

Black Sand Basin is a geothermal area in the Upper Geyser Basin within Yellowstone National Park, featuring multiple hot springs and geysers with varying temperatures. The pools display different colors from turquoise to blue depending on mineral content and water depth.

A. C. Peale named the area Emerald Group in 1878, after Emerald Pool. Visitors began calling it Black Sand Basin for the obsidian sand covering much of the ground, and that name stuck. The basin's former main draw was Handkerchief Pool, where currents carried dropped handkerchiefs away and returned them cleaned.

The name Black Sand Basin comes from the obsidian sand that darkens the ground around the springs. The basin was first called Emerald Group, a name A. C. Peale gave it in 1878 after Emerald Pool, but the tourists' name prevailed. Visitors once dropped handkerchiefs into Handkerchief Pool and watched the currents carry them down and return them cleaned.

You can reach the area by a short walk from the parking area or connect from Daisy Geyser nearby, with trails open year-round. Wear sturdy shoes since paths can be uneven and stay behind barriers near hot springs.

Handkerchief Pool, once the basin's main draw, pulled handkerchiefs under and returned them cleaned; the practice has ended. The basin also holds Cliff Geyser at 191.8 °F (88.8 °C) and Spouter Geyser at 199.9 °F (93.3 °C), and in winter a marked ski trail links it to the Old Faithful Visitor Center.