Nuclearites are hypothetical, massive particles of Strange Quark Matter (SQM) introduced by E. Witten in 1984. They are composed of approximately equal quantities of up, down, and strange quarks. Due to the third quark flavor component which leads to a total energy lower than in the case of nuclear matter, SQM could represent the ground state of Quantum Chromodynamics (QCD). The detection and characterization of nuclearites could also bring important contributions to the Dark Matter physics.
KM3NeT is a network of deep-sea neutrino telescopes placed in the Mediterranean Sea, optimized for the search for high-energy cosmic neutrinos (KM3NeT/ARCA) and the study of neutrino properties with atmospheric neutrinos (KM3NeT/ORCA). Nuclearites above a mass threshold of $10^{13}$ GeV/c$^2$ having velocities of approximately 250 km/s could reach the ground and interact in the detector through elastic collisions. A fraction of the energy generated in these collisions is dissipated as visible blackbody radiation. A customized Monte Carlo (MC) program was used to simulate the propagation and the signal of nuclearites inside the KM3NeT detector. The background considered for this study is represented by the $^{40}$K decay, which is added during the filtering stage of the MC output, and by the simulated atmospheric muons. The analysis uses selection cuts in order to remove the main background of atmospheric muons and to estimate the sensitivity of the detector. Preliminary results on the sensitivity of the KM3NeT neutrino telescope to a flux of massive down-going nuclearites will be presented.