Trinitite, also known as Atomite or Alamogordo Glass, is the name given to the glassy residue left on the desert floor after the plutonium-based Trinity nuclear bomb test July 16, 1945, near Alamogordo, New Mexico. The glass is primarily composed of silica and feldspar that was melted by the atomic blast. It is usually a light green color, although in some cases it is other colors. It is mildly radioactive, but is safe to handle for limited periods of time.[1][2]
In the late 1940s and early 1950s, samples were gathered and sold to mineral collectors as a novelty. Traces of the material can be found at the Trinity Site today, though most of it was bulldozed and buried by the United States Atomic Energy Commission in 1952. 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.

In 2005 it was theorized by Los Alamos National Laboratory scientist Robert Hermes and independent investigator William Strickfaden that much of the mineral was formed not simply by sand which was exposed to the fireball, but the sand which was drawn up inside the fireball itself and then rained down in a liquid form.[3]

A number of different types of Trinitite have been identified. Green is the most common form. Black contains iron from the tower structure. Red contains copper from the 'gadget' itself or from the communications cables that led away from the site. Rounded pearls are also found which come from melted silica that returned to solid form before hitting the ground.

The name Trinitite is occasionally broadly applied to all glassy residues of nuclear bomb testing, not just the Trinity test. There are many known fakes in circulation among collectors. These fakes use a variety of means to achieve the glassy green silica look as well as mild radioactivity. However, only trinitite from a nuclear explosion will contain certain neutron activation products which are not found in naturally radioactive ores and minerals. In addition, more detailed gamma spectroscopy can narrow down the potential nuclear explosions from which the material formed.

wikipedia.org

Types of Trinitite
GREEN TRINITITE
Green Trinitite was the most abundant, and therefore gives reason as to why the collector even these days can still locate a respectable piece of green Trinitite for sale,
although even this is becoming more and more harder to find. The color is attributed to its content of iron.
Below each image of green Trinitite, I have included the specimen’s Spectrum Analysis
to show the evidence of fission byproducts still present in the specimens:

RED TRINITITE

Red Trinitite, rarely seen and highly collectible, is practically impossible to find by the collector and if found would demand a higher price. The color according to various sources and studies is attributed to its high content of copper. Red Trinitite such as this is due to copper inclusion from the wiring of the “gadget” itself or from the many communication cable wiring that was used in the test
itself

BLACK TRINITITE
Black Trinitite-This color of Trinitite as far from a collector’s standpoint, is hardly ever seen or obtained. I acquired one small piece for my collection from a private source &
collector who had access to the site during the days when obtaining trinitite at the test site was a possibility. The deep color of a dark black is of course mainly attributed to the
content of iron also, it has been mentioned from the tower itself?