Lechatelierite is silica glass, amorphous SiO2. Lechatelierite forms due to very high temperature melting of quartz sand caused by a lightning strike. The result is an irregular, branching, often hollow tube of silica glass. These tubes are also called fulgurite by mineral collectors.

Lechatelierite also forms as the result of high pressure shock metamorphism during meteorite impacts known as tektites. Most tektites are blebs of impure glassy material, but tektites from the Sahara in Libya and Egypt are of pure silica and known as Libyan desert glass. A unique example of lechatelierite was formed by the first nuclear bomb explosion at Trinity Flats, White Sands, New Mexico. Samples from this event are called trinitite.

High pressure experiments have shown that pressures of 85 GPa are needed to produce lechatelierite in the quartz grains of the granite samples tested.

Lechatelierite is a mineraloid as it does not have a crystal structure. Although not a true mineral, it is often classified in the quartz mineral group.