Natural MoS2 is an indirect gap semiconductor (1.2 eV) but becomes highly luminescent in the monolayer from at 1.9 eV (quasi-particle / optical band gap). Natural crystals are lower grade compared to our SYNTHETIC MOS2 CRYSTALS in terms of purity, defect concentration, and crystallinity. These natural source MoS2 crystals come in different sizes ranging from SMALL to LARGE MoS2. In their untouched form, they contain large amount of impurities such as Fe, O, Cr, Ni, C, Se, P, and Si. These natural source crystals undergo a number of cleaning process to eliminate these impurities from the edges, surfaces, macroscale defect sites, as well as macroscopic cracks within the specimen. During this process, approximately 90% of the crystal is eliminated to bring you only the clean pieces for research use.