Did this in Grade 10 to an Ice Cream cart ( we were being exploited as underage workers, at least that is the story the Judge bought). Buddy and I crunched briquettes ( charcoal ), and bought saltpetre from the pharmacy in large tubs. The Pharmacist actually asked " You boys aren't making fireworks, are you?" My more worldly friend replied "No, sir my mom wants me to buy it as a special ingredient in her cooking, but it is a secret to dad."
Only years later did I learn the biological uses of saltpetre.
Sulphur ( as the "1" in the 3-3-1) was readily available, but not dripping out of hillocks. Tubes are easy to find, especially if you have only a Grade 10 notion of pressure and safety.
Oh, and the diamonds? My friends moms jewelry and a disassembled chandelier.
We got in so much sh*t we thought the world had ended.