minecraft-assets/assets/minecraft/advancements/story/mine_diamond.json

{
    "display": {
        "icon": "minecraft:diamond",
        "title": "Diamonds!"
    },
    "parent": "minecraft:story/iron_tools",
    "criteria": {
        "diamond": {
            "trigger": "minecraft:inventory_changed",
            "conditions": {
                "items": [
                    {
                        "item": "minecraft:diamond"
                    }
                ]
            }
        }
    }
}