  Infrared and ultraviolet observations of nova light curves have confirmed
grain formation in their expanding shells that are ejected into the
interstellar medium by a thermonuclear runaway. In this paper, we present
isotopic ratios of intermediate-mass elements up to silicon for the ejecta of
CO and ONe novae, based on 20 hydrodynamic models of nova explosions. These
theoretical estimates will help to properly identify nova grains in primitive
meteorites. In addition, equilibrium condensation calculations are used to
predict the types of grains that can be expected in the nova ejecta, providing
some hints on the puzzling formation of C-rich dust in O>C environments. These
results show that SiC grains can condense in ONe novae, in concert with an
inferred (ONe) nova origin for several presolar SiC grains.
