18 Karat (18K) gold contains 18 parts gold out of 24, with the remaining 6 parts made up of carefully selected alloying metals to enhance strength, hardness, wear resistance, and color control.
With a gold content of 75.00%, 18K gold is the most widely used premium jewelry grade globally, offering an optimal balance between luxury appearance and practical durability.
Purity & Grade Classification
| Karat | Gold Content | Fineness |
|---|---|---|
| 18K | 75.00% Au | 750 |
| 22K | 91.67% Au | 916 |
| 24K | 99.9 – 99.99% Au | 999 |
| 14K | 58.50% Au | 585 |
Industry Markings:
✔ 750
✔ 75% Au
✔ 18K
Strengthening & Metallurgical Behavior
Crystal Structure: Face-Centered Cubic (FCC) gold-based solid solution.
Strengthening Mechanisms:
✔ Solid-solution strengthening from Cu, Ag, Ni, Pd
✔ Work hardening during rolling, forming, and setting
✔ Limited age-hardening in certain Cu-rich compositions
Refining & Processing Properties
Manufacturing Routes:
• Alloy melting & precision casting
• Rolling, stamping, and forging
• CNC machining for components
• Polishing and surface finishing
• Rhodium plating for white gold
Recycling:
• Highly recyclable with minimal losses
• Alloy chemistry adjustable during refining
• Gold recovery efficiency > 99.9%
Available Forms of 18K Gold
✔ Fine jewelry (rings, necklaces, bracelets)
✔ Watch cases and luxury accessories
✔ Medals and decorative items
✔ Limited-edition coins and medallions
Applications
Jewelry:
• Engagement and wedding rings
• Gemstone settings
• Designer and luxury collections
Luxury Goods:
• Watch cases
• Premium writing instruments
Industrial / Technical:
• Electrical contacts (select applications)
• Decorative and functional coatings
Advantages of 18K Gold
✔ Stronger and harder than 22K and 24K gold
✔ Excellent gemstone holding capability
✔ Wide color range (yellow, white, rose, green)
✔ High prestige and global acceptance
✔ Long-term durability for daily wear
Limitations of 18K Gold
⚠ Lower gold content than 22K or 24K by weight
⚠ Slightly reduced resale value per gram of gold
⚠ White gold may require periodic rhodium re-plating
Why Choose 18K Gold?
Choose 18K gold when:
✔ Daily-wear durability is required
✔ Gemstones are involved
✔ Color customization is desired
✔ Luxury appearance with mechanical strength is important
Avoid 18K gold when:
• Maximum gold purity is the primary objective
• Cultural preference favors higher karat gold
In summary: 18 Karat (18K) gold, graded as 750 fine gold, represents the ideal balance between purity and performance. With enhanced mechanical strength, excellent wear resistance, and outstanding design flexibility, it is the global standard for fine jewelry and luxury goods.