The gold used in jewelry is almost never in its pure form, known as 24-karat gold. Pure gold is naturally soft and highly malleable, meaning it can be easily scratched, bent, and worn down with regular use. To create a material suitable for everyday wear, the gold must be mixed with other metals through a process called alloying, which provides the necessary strength and durability.
Defining Karat Purity
The purity of gold is measured using the karat system, which is based on a fraction of 24 parts. A piece of gold jewelry is considered 24 karat (24k) if all 24 parts are pure gold, signifying 100% gold content. The 14k designation means that 14 parts of the total 24 parts are pure gold, with the remaining 10 parts consisting of other metals.
This translates to a gold content of 58.3% by weight, which is why 14k gold is often stamped with the number “585” in Europe and other regions. For context, 18k gold is 75% pure gold (18 out of 24 parts), offering a richer color but being slightly softer. Conversely, 10k gold contains only 41.7% pure gold, making it the hardest and most budget-friendly option, though it has the lowest gold content.
The Essential Alloying Metals
The remaining 41.7% of a 14k gold piece is a carefully balanced mixture of other metals, primarily Copper (Cu), Silver (Ag), Nickel (Ni), and Zinc (Zn). The exact ratio of these metals determines the final color and physical properties of the gold alloy. For standard 14k yellow gold, the non-gold portion is typically a combination of silver and copper, often with a small amount of zinc.
Copper is the primary hardening agent and contributes a reddish hue to the alloy, while silver is added to lighten the color and improve the metal’s workability. Zinc is generally included in small percentages to act as a deoxidizer during the casting process and further increase the alloy’s hardness. The specific blend is adjusted by the metallurgist to achieve the desired tone and mechanical strength.
Rose gold alloys rely on a higher proportion of copper to achieve their signature pinkish-red color, with silver used to fine-tune the shade. White gold, however, uses different alloying metals like nickel, palladium, or manganese to bleach the gold’s natural yellow color.
How Alloys Influence Color and Durability
The addition of base metals dramatically increases the durability of 14k gold, making it highly resistant to scratching and denting. The alloys create a much stronger lattice structure than pure gold, allowing the jewelry to maintain its shape and finish over time. This enhanced hardness makes 14k gold a popular choice for engagement rings and wedding bands.
The most noticeable effect of alloying is the modification of the gold’s color. The deep red color of copper gives rise to rose gold, a blend that is often more durable than yellow gold due to its high copper content. White gold uses nickel or palladium to impart a silvery-white appearance, though it is usually finished with a rhodium plating to achieve a bright, reflective white surface.
A significant consideration with alloying is the potential for metal sensitivities, particularly concerning nickel. Nickel is a common allergen, and because it is frequently used in white gold alloys, it can cause contact dermatitis in some wearers. Reputable jewelry manufacturers offer nickel-free white gold options, which typically substitute palladium to mitigate this health concern.