This colourless salt is an intermediate in the isolation of thallium from its ores.

The resulting TlCl precipitate is separated by filtration of the reaction mixture.

The crystalline structure is of cubic caesium chloride type at room temperature, but it lowers to the orthorhombic thallium iodide type upon cooling, the transition temperature being likely affected by the impurities.

[6] Nanometer-thin TlCl films grown on KBr substrates exhibit a rocksalt structure, while the films deposited on mica or NaCl are of the regular CsCl type.

[7] A very rare mineral lafossaite, Tl(Cl,Br), is a natural form of thallium(I) chloride.