Copper(I) iodide
Copper iodide is the inorganic compound
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...

 with the formula CuI. It is also known as cuprous iodide. It is useful in a variety of applications ranging from organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...

 to cloud seeding
Cloud seeding
Cloud seeding, a form of intentional weather modification, is the attempt to change the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud...


Copper(I) iodide is white, but samples are often tan or even, when found in nature as rare mineral marshite, reddish brown, but such color is due to impurities. It is common for samples of iodide-containing compounds to become discolored because of the easy aerobic oxidation of the iodide anion to iodine.
Copper(I) iodide, like most "binary" (containing only two elements) metal halides, is an inorganic polymer.