The compound is a bright yellow solid, but samples almost always contain impurities of metallic silver that give a grey colouration.

Alternatively, dissolution of AgI in a solution of concentrated silver nitrate followed by dilution affords α-AgI.

[10] Unless the preparation is conducted in dark conditions, the solid darkens rapidly, the light causing the reduction of ionic silver to metallic.

The crystalline structure of β-AgI is similar to that of ice, allowing it to induce freezing by the process known as heterogeneous nucleation.

[citation needed] Extreme exposure can lead to argyria, characterized by localized discolouration of body tissue.