The standard density and average atomic weights of hypothetical materials c
ontained in the inner layers of the Earth are calculated from results of sh
ock-wave studies using a previously proposed method for determining the vel
ocity of sound in materials at high pressures and density, and from seismic
data. These data turned out to be sufficient to refine the elemental compo
sition of the Earth's interior. It is shown that the iron-nickel core of th
e Earth should contain approximate to 10% (by weight) carbon, partly ill th
e diamond phase. According to the calculations, the lower mantle can contai
n up to 20% carbon, which probably comes front the core.