Circumstellar dust can be responsible for significant extinction and is usually the source of an infrared excess for stars that have it.
[1] According to a study, it is still uncertain whether the dust is a result of crystalline silicate or polycyclic aromatic hydrocarbon.
[2] It is suggested that the circumstellar dust components can depend on the evolutionary stage of a star and is related to the changes in its physical conditions.
The circumstellar dust around aging stars has been observed to include, "almost pure crystalline Mg-rich silicates (forsterite and clinoenstatite), amorphous silicates, diopside, spinel, oxides (corundum and Fe0.9Mg0.1O), and also carbon-rich solids such as: (hydrogenated) amorphous carbons, aromatic hydrocarbons and silicon carbide.
"[4] The motion of circumstellar dust is governed by forces due to stellar gravity and radiation pressure.