We review observed properties of dust surrounding both hot and cool massive stars. The chemical composition of the dust provides information on the chemical and physical conditions at the time of dust formation, and the geometry of the dust envelope can be used to study the physics of the wind and the interaction between previous and current mass loss. Crystalline silicates may be used as a tracer of very high mass-loss phases of massive stars. Mixed chemistry of both oxygen-rich and carbon-rich dust is observed both in hot and cool massive stars.