ZnS particles prepared by depositing a colloidal ZnS suspension on highly ordered pyrolytic graphite surfaces and Au(110) surfaces were investigated by scanning tunneling microscope (STM). STM directly imaged the particles in real space and measured their dimensions to be 1-5 nm despite the 3.82 eV bulk band gap of ZnS material. The surface atomic topography of a single ZnS particle was also obtained by STM. The periodic arrangement of surface atoms was easily seen, which indicates that ZnS particles are crystallites. Vacancy defects were also found on ZnS dried particle surfaces, which can produce surface states. It was also found that several small crystallites can aggregate to form clusters that lead to different shapes and sizes. The clusters can also aggregate to form lumps. Since ZnS particles and small clusters can easily be moved by the STM tip, it can be seen that no serious reactions exist between ZnS and the substrate surfaces. Some clusters were found to be unstable and can fall apart during tip scanning.