手册:Minecraft:spawns on block filter

应填在"conditions"下方，中括号内填写允许进行生成尝试的方块

{
    "conditions": [
        {
            "minecraft:spawns_on_block_filter": [
                "minecraft:stone",
                "minecraft:snow",
                "minecraft:powder_snow",
                "minecraft:snow_layer",
                "minecraft:packed_ice",
                "minecraft:gravel"
            ]
        } 
    ]
}