Full configuration interaction calculations demonstrate the existence of mixed correlation phases in truly three-dimensional elongated nanocrystals subject to inhomogeneous spatial confining potentials. In such phases, the electron density behaves like a Fermi liquid in some regions, while, simultaneously, other more dilute regions display the typical quasi-classical Wigner distribution. The present results confirm and strengthen previous local spin-density functional theory predictions [Ballester et al., Phys. Rev. B 82, 115405 (2010)]. Additionally, simulation of the in-plane and z-polarized modes of the absorption spectra reveals the different correlation regimes occurring in these systems.