Abstract This chapter discusses the composition of protoplanetary dust as derived from laboratory analysis of Solar System dust and from infrared remote sensing of protoplanetary dust around young stars. The advantages, disadvantages and limitations of different laboratory and remote sensing techniques used to derive compositional information are discussed in some detail. Also, an overview is given of the current state of knowledge of both the chemical and mineralogical composition of the dust. Finally, we briefly touch upon some of the implications of the findings for our understanding of the formation and processing history of the grains.

In this chapter we focus on the composition of protoplanetary and Solar System cosmic dust. This composition is important for at least two reasons. First, it provides us with a view on the origin of planets, asteroids, and comets. Second, and maybe even more importantly, the composition of dust can be used as a tracer of dynamical processes taking place in the protoplanetary disk. Certain dust species can only be formed under special circumstances, at certain temperatures or densities. Finding these species outside of their formation area allows us to trace disk dynamics.

So what do we mean by dust composition? We will address in this chapter both the chemical and the mineralogical composition, since these are both important in terms of tracing the thermal history of the grains. The mineralogical composition, i.e. the lattice structure or absence thereof, is one of the key characteristics used in current remote sensing of cometary and protoplanetary dust.