The crystal structure of smithsonite belongs to the trigonal system. Single crystal is rhombohedral or ditrigonal-scalenohedral, which however is extremely rare. And normally it is the aggregates of shapes of stalactite, lump, earth, and hull. The pure one is white but often dyed gray, yellow, light green or light brown. It is from transparent to translucent, and with gloss of glass or dull earthy luster. And sometimes there is soft luster of pearls on the crystal surface. Hardness is from 4.5 to 5. It is brittle and irregular-shaped fracture surface. Relative density is from 4 to 4.5.
Main chemical compositions of smithsonite are zinc carbonate (ZnCO3). In addition, it still contains 0.27% calcium oxide (CaO), 0.45% magnesium oxide (MgO), 0.58% iron oxide (Fe2O3), and 0.01% manganese oxide (MnO). Among them zinc is often replaced by iron (bivalent). And some still contains a small amount of cobalt, copper, cadmium, lead, and trace amounts of germanium and indium.