Since a “mixed” train refers to a mixed freight/passenger train, a common term for a freight that includes a mix of different cars is “manifest.”
What cars are in that manifest depends entirely on the origin and destination yards, and the industries or interchanges and connections at each end or in between. Grain is extremely common on many roads, indeed on some praririe lines it may be the primary or only cargo carried, while on the Algoma Central there was absolutely zero grain traffic, as it was a northern Ontario shortline that served primarily forestry and iron ore traffic and finished steel from a mill in Sault Ste Marie to connections with the CN and CP.
Our club layout by contrast, has a huge variety of traffic and cargoes. Local traffic includes lots of covered hoppers of cement, tankcars of sulphuric acid, fuel oil, gasoline, diesel and chlorine, boxcars of paper and woodpulp, and LCL for the freight shed, hoppers of gravel, crushed slag (for track ballast), coal and iron ore pellets, as well as gondolas of steel products, flatcars of pulpwood and lumber and nickel ore in various forms (raw ore in 20’ ore cars, ore concentrates in covered gondolas, processed nickel matte in covered hoppers and and semi-processed concentrated nickel ore/water slurry in specialized cars).
The area represented by the club layout is also located on CP’s main transcontinental route, and everything going cross-country passes through. Therefore through traffic includes everything from lumber and telephone poles from BC and Alberta, potash and grain from Alberta, Saskatchewan and Manitoba, steel from mills in Regina, Selkirk (near Winnipeg), Sault Ste Marie and Hamilton (near Toronto), paper from other Ontario and Quebec mills, livestock and frozen meat from Alberta, beer, manufactured goods, automobiles, chemicals and plastics from Ontario and Quebec, as well as intermodal, large amounts