Well, to be technical [industrial chemist hat on
] here; the components are the carbonaceous fuel/sensitiser [there are good practical reasons to use diesel], and the inorganic chemical oxidising agent.
Mixtures of these components which can achieve high-order detonation [i.e. > the speed of sound] are technically termed 'Sprengel explosives', after an early development chemist.
The AN/FO mix technology was first introduced in the 1950's, in the USA. The actual mix ratio is quite critical to achieving maximum power, and velocity of detonation.
Edit:The first major project to use ANFO in Oz on a large scale was the Snowy Mountains Hydro Scheme, in hard rock blasting for their tunnels and underground power station turbine halls.
However, earlier Sprengel explosives [e.g. 'Rackarock' was in common use in Oz] were in use by the late 19th century.
'Ag grade' Nitropril is/was just ICI's fertiliser grade of prilled [that bit is important] Ammonium Nitrate [AN], and was dyed pink. 'Explosive grade' Nitropril isn't dyed.
But for many uses, the then cheaper Ag grade worked just as well - that's what I used to use.
I've seen pink AN prills in sticks of the old AN60 Gelignite - so ICI used the Ag grade there at times, too!
