[
  {
    "karat": 24,
    "fineness": 999,
    "color": "yellow",
    "name": "24K Yellow Gold",
    "composition_percent": {
      "gold": 99.9
    },
    "density_g_cm3": 19.32,
    "melting_point_c": 1064,
    "notes": "Pure gold. Used for bullion and East Asian bridal pieces. Too soft for most Western jewelry."
  },
  {
    "karat": 22,
    "fineness": 916,
    "color": "yellow",
    "name": "22K Yellow Gold",
    "composition_percent": {
      "gold": 91.67,
      "silver": 5,
      "copper": 3.33
    },
    "density_g_cm3": 17.7,
    "melting_point_c": 977,
    "notes": "Indian and Middle Eastern standard. Bright yellow, soft. Common in heirloom-style designs."
  },
  {
    "karat": 18,
    "fineness": 750,
    "color": "yellow",
    "name": "18K Yellow Gold",
    "composition_percent": {
      "gold": 75,
      "silver": 12.5,
      "copper": 12.5
    },
    "density_g_cm3": 15.45,
    "melting_point_c": 905,
    "notes": "Premium standard worldwide. Warm rich yellow tone. Copper-to-silver ratio adjusted for tone and casting properties."
  },
  {
    "karat": 18,
    "fineness": 750,
    "color": "white",
    "name": "18K White Gold (palladium-based)",
    "composition_percent": {
      "gold": 75,
      "palladium": 25
    },
    "density_g_cm3": 15.1,
    "melting_point_c": 1310,
    "notes": "Nickel-free white gold. Hypoallergenic. More expensive than nickel-white due to palladium content. Off-white tone; often rhodium-plated."
  },
  {
    "karat": 18,
    "fineness": 750,
    "color": "white",
    "name": "18K White Gold (nickel-based)",
    "composition_percent": {
      "gold": 75,
      "copper": 10,
      "nickel": 10,
      "zinc": 5
    },
    "density_g_cm3": 14.7,
    "melting_point_c": 940,
    "notes": "Traditional white gold formulation. Whiter than palladium variant. Nickel can trigger contact allergy — regulated in EU under REACH. Banned in some markets."
  },
  {
    "karat": 18,
    "fineness": 750,
    "color": "rose",
    "name": "18K Rose Gold",
    "composition_percent": {
      "gold": 75,
      "copper": 22.25,
      "silver": 2.75
    },
    "density_g_cm3": 15.5,
    "melting_point_c": 895,
    "notes": "Warm pink-red hue from high copper content. Common bridal alternative since 2010s. Sometimes called 'red gold' (highest-copper) or 'pink gold' (more silver, paler)."
  },
  {
    "karat": 18,
    "fineness": 750,
    "color": "pink",
    "name": "18K Pink Gold (Japanese style)",
    "composition_percent": {
      "gold": 75,
      "copper": 18,
      "silver": 5,
      "palladium": 2
    },
    "density_g_cm3": 15.4,
    "melting_point_c": 905,
    "notes": "Softer, paler pink than Western rose gold. Standard Japanese bridal pink gold (K18PG). Reduced copper content for cooler tone."
  },
  {
    "karat": 18,
    "fineness": 750,
    "color": "green",
    "name": "18K Green Gold (electrum)",
    "composition_percent": {
      "gold": 75,
      "silver": 25
    },
    "density_g_cm3": 15.6,
    "melting_point_c": 1010,
    "notes": "Pale greenish tint from high silver / no copper. Rare; used as accent in multi-color gold pieces."
  },
  {
    "karat": 14,
    "fineness": 585,
    "color": "yellow",
    "name": "14K Yellow Gold",
    "composition_percent": {
      "gold": 58.5,
      "silver": 25,
      "copper": 16.5
    },
    "density_g_cm3": 13.4,
    "melting_point_c": 882,
    "notes": "Dominant US standard. Harder and more durable than K18; slightly less saturated yellow. Most common US engagement-ring metal."
  },
  {
    "karat": 14,
    "fineness": 585,
    "color": "white",
    "name": "14K White Gold (nickel-based)",
    "composition_percent": {
      "gold": 58.5,
      "copper": 21,
      "nickel": 12.5,
      "zinc": 8
    },
    "density_g_cm3": 12.8,
    "melting_point_c": 945,
    "notes": "Traditional US-market white gold. Strong, durable, less expensive than palladium-based. Nickel allergy risk."
  },
  {
    "karat": 14,
    "fineness": 585,
    "color": "white",
    "name": "14K White Gold (palladium-based)",
    "composition_percent": {
      "gold": 58.5,
      "palladium": 27,
      "silver": 14.5
    },
    "density_g_cm3": 13.0,
    "melting_point_c": 1260,
    "notes": "Premium hypoallergenic white gold. More common in EU and for nickel-sensitive customers."
  },
  {
    "karat": 14,
    "fineness": 585,
    "color": "rose",
    "name": "14K Rose Gold",
    "composition_percent": {
      "gold": 58.5,
      "copper": 31,
      "silver": 10.5
    },
    "density_g_cm3": 13.6,
    "melting_point_c": 855,
    "notes": "Stronger pink tone than K18RG due to lower gold percentage. Affordable and durable."
  },
  {
    "karat": 10,
    "fineness": 417,
    "color": "yellow",
    "name": "10K Yellow Gold",
    "composition_percent": {
      "gold": 41.7,
      "silver": 14,
      "copper": 39,
      "zinc": 5.3
    },
    "density_g_cm3": 11.6,
    "melting_point_c": 876,
    "notes": "US minimum-karat gold. More durable than higher karats but paler yellow. Common in class rings and budget bridal."
  },
  {
    "karat": 10,
    "fineness": 417,
    "color": "white",
    "name": "10K White Gold",
    "composition_percent": {
      "gold": 41.7,
      "copper": 25,
      "nickel": 20,
      "zinc": 13.3
    },
    "density_g_cm3": 11.3,
    "melting_point_c": 925,
    "notes": "Common US-market budget white gold. Almost always rhodium-plated. Nickel allergy risk."
  },
  {
    "karat": 9,
    "fineness": 375,
    "color": "yellow",
    "name": "9K Yellow Gold",
    "composition_percent": {
      "gold": 37.5,
      "silver": 18,
      "copper": 37,
      "zinc": 7.5
    },
    "density_g_cm3": 11.1,
    "melting_point_c": 880,
    "notes": "UK / Commonwealth minimum 'gold'. Brassier yellow than higher karats. Below US gold-legality threshold."
  }
]