A study was conducted to investigate the properties of weakly bound clusters of single-digit nanodiamonds (SND) using spectrally and temporally resolved luminescence detection, electron paramagnetic resonance (EPR) spectroscopy, and transmission electron microscopy (SEM). Nitrogen-vacancy (NV) centers were created in diamonds by high-energy proton irradiation followed by thermal annealing. Samples containing equal weights of 55-nm HTHP diamonds and SNDs were uniformly distributed on quartz substrates for luminescence measurements. It was observed that the SNDs exhibited significant luminescence in the red spectral region before irradiation. The emission was blue-shifted and the absence of the zero-phonon lines at 637 and 575 nm indicated that the luminescence did not originate from NV centers as compared with the NV spectrum.