  Considering the low-temperature ($T$) and high-baryon-number-density ($n_B$)
region of the QCD phase diagram, we present a model for the first-order phase
transition between the quark-gluon plasma (QGP) and the recently proposed
colour superconducting phase. We study nucleation of a droplet of the
superconducting phase within the metastable QGP gas. Numerical results for the
activation energy, radius and other physical parameters of the droplets, at
various temperatures, densities and gap parameters, are given. We have
estimated the latent heat of the phase transition. In the $T-n_B$ plane, we are
able to demarcate the region of the superconducting phase.
