{
  "feature": "ageofthegods:gravel_boulder",
  "placement": [
    {
      "type": "minecraft:count",
      "count": 1
    },
    {
      "type": "minecraft:in_square"
    },
    {
      "type": "minecraft:heightmap",
      "heightmap": "WORLD_SURFACE_WG"
    },
    {
      "type": "minecraft:block_predicate_filter",
      "predicate": {
        "type": "minecraft:matching_blocks",
        "blocks": "minecraft:granite",
        "offset": [
          0,
          -1,
          0
        ]
      }
    },
    {
      "type": "minecraft:biome"
    }
  ]
}