, also known as atomsite or Alamogordo glass,^[2] is the glassy residue left on the desert floor after the plutonium-based Trinity nuclear bomb test on July 16, 1945, near Alamogordo, New Mexico. The glass is primarily composed of arkosic sand composed of quartz grains and feldspar (both microcline and smaller amount of plagioclase with small amount of calcite, hornblende and augite in a matrix of sandy clay)^[3] that was melted by the atomic blast. It is usually a light green, although color can vary. It is mildly radioactive but safe to handle.^[4][5][6]

In the late 1940s and early 1950s, samples were gathered and sold to mineral collectors as a novelty. Traces of the material may still be found at the Trinity Site as of 2019, although most of it was bulldozed and buried by the United States Atomic Energy Commission in 1953.^[7] It is now illegal to take the remaining material from the site; however, material that was taken prior to this prohibition is still in the hands of collectors.