Let's take for example you want a 50%/50% chance of either getting diamonds or dirt:
yellow-crystal: # your custom blocks
settings:
items-to-inventory: true
directly-bedrock: true
stages:
1:
material: "YELLOW_CONCRETE"
step-time: 4
drops:
diamonds: #this can be anything i suggest naming it as you want
chance: 50
actions:
- "[give-item] DIAMOND 64"
dirt:
chance: 50
actions:
- "[give-item] DIRT 64"
2:
material: "YELLOW_STAINED_GLASS"
step-time: 4
yellow-crystal:
settings:
items-to-inventory: true
directly-bedrock: true
stages:
1:
material: "YELLOW_CONCRETE"
step-time: 4
drops:
very_rare_drop: #this can be anything I suggest naming it as you want
chance: 1
actions:
- "[give-item] DIAMOND 64"
nothing:
chance: 99
actions: []
2:
material: "YELLOW_STAINED_GLASS"
step-time: 4