minecraft-assets/data/minecraft/worldgen/configured_feature/ore_gravel_nether.json

{
  "type": "minecraft:ore",
  "config": {
    "discard_chance_on_air_exposure": 0.0,
    "size": 33,
    "targets": [
      {
        "state": {
          "Name": "minecraft:gravel"
        },
        "target": {
          "block": "minecraft:netherrack",
          "predicate_type": "minecraft:block_match"
        }
      }
    ]
  }
}