Trinitite sample at Trinity Site, New Mexico, USA. This artificial mineral was formed when the worldIllustrations first nuclear bomb was tested at this site on the 16th of July 1945, as part of the Manhattan Project. Trinitite is an altered silicate resembling rough green glass. The extreme temperatures of the nuclear explosion melted the native sandstone soil. As the material cooled it formed a glassy structure. The greenish colour comes from iron in the sand. It has lost most of its radioactivity and is safe to handle, though removal from the Trinity test site is prohibited by the US army.