Gold Alloys Guide – Composition, Types & Uses

Gold is valued for its beauty and corrosion resistance, but in its pure form, it’s also very soft and easily damaged. In fact, it’s so malleable that a single gram of it can be spread into a sheet covering nearly one square metre. That’s why most gold used in jewellery, coins, and decorative items is mixed with other metals to create gold alloys.

These alloys, made by mixing gold with metals like zinc, copper, and silver, not only make gold stronger and more durable, but they can also change its colour and properties. In this gold alloys guide, we’ll explore what gold alloys are, how they’re made, and the most common gold alloys you’ll see today.

What is gold purity?

Gold purity is measured in carats (or karats, abbreviated ‘k’ in the U.S.) in parts of twenty four. Pure gold is 24 carats (24ct), meaning it contains 99.99% gold with no other metals mixed in.

Gold purity can also be measured in fineness, which represents parts per thousand. For example, 999 fineness refers to 99.9% pure gold, while 9999 fineness is gold that’s 99.99% pure.

Lower carat gold contains a mix of gold and other metals to create an alloy. These alloys can improve the strength and durability of gold while also changing its colour. While carat ratings tell you how much gold is in an alloy, they don’t specify which other metals are included.

The table below summarises the different gold carat ratings:

CARAT (CT)	GOLD PURITY	HALLMARK
24ct	99.9%	999
22ct	91.6%	916
20ct	83.3%	833
18c	75%	750
14ct	58.3%	583/585
10ct	41.7%	417

Keep Reading: Gold Purity, Fineness, And Karat – What Is It And How To Check It

Most common gold alloys

Pure 24-carat gold is naturally bright yellow. Beyond its use in investment-grade gold bullion bars and coins, pure gold is often too soft and malleable for jewellery and other applications. Instead, it’s alloyed with other metals to increase durability, change its colour, and make it more resistant to wear.

The most common metals combined with gold include copper, silver, zinc, platinum, palladium, nickel, and iron. Gold alloys typically fall into four main categories: yellow, white, rose, and green, but many other unique shades exist.

Let’s take a look at the most common gold alloys.

Image: https://www.bullionbypost.co.uk/index/gold/gold-alloys/

Yellow gold

Traditional yellow gold is an alloy of gold, silver, and copper. The silver helps maintain the gold’s signature yellow hue and the copper adds durability. This blend keeps gold durable enough for daily wear while preserving its classic golden luster.

Higher carat yellow gold (like 22ct and 18ct) retains a deeper, richer gold tone due to its higher gold content, while lower carat yellow gold (14ct or 10 ct) has a paler shade because of the increased presence of alloy metals.

For example, 22-carat yellow gold might be made from:

• 91.67% gold
• 5% silver
• 2% copper
• 1.33% zinc.

White gold

White gold is popular for its sleek, modern appearance and brilliant shine. It’s created by alloying gold with white metals like nickel, palladium, platinum, and zinc. The most common mix is 75% gold with 25% platinum or palladium, resulting in a silvery-white metal.

Because gold is naturally yellow, most white gold alloys will retain a slight yellowish tint. To counter this, white gold is often rhodium-plated. This achieves that bright white finish often seen in jewellery stores and adds extra durability. However, the rhodium plating can wear off over time, requiring reapplication every few years to keep that bright white colour.

Rose gold

Rose gold, sometimes called pink gold, has a warm, rosy hue that comes from its copper content. The higher the copper content, the deeper the red tone. Rose gold is durable and doesn’t require additional plating, making it a long-lasting choice for gold jewellery.

An example composition of 18-carat gold rose might be:

• 75% gold
• 22.25% copper
• 2.75% silver.

Green gold (electrum)

Green gold is less common these days, but has been used for thousands of years since it’s a naturally occurring alloy. Green gold is a combination of gold and silver, also known as electrum. It was commonly used by ancient civilisations for jewellery – and some Egyptian pyramids are even capped with a layer of it.

Green gold’s pale yellow-green tint comes from the silver content. Some modern variations include zinc or cadmium, but cadmium is rarely used today due to toxicity concerns.

Keep Reading: What is Gold Carat?

Rare and less common gold alloys

Beyond the standard yellow, white, rose, and green golds, jewellers can create unique shades by adjusting the compositions of gold alloys. These include:

• Red gold: Similar to rose gold, but with a deeper, richer colour due to an even higher percentage of copper. Eliminating silver from the mix results in a more intense red.
• Purple gold: An alloy of 80% gold and 20% aluminium that forms a violet-coloured metal. However, it’s brittle and can shatter under impact, which makes it impractical for regular use.
• Blue gold: Created with 75% gold and 25% iron, giving it a steely blue hue. Like purple gold, blue gold is fragile and not commonly used in jewellery.
• Grey gold: A mix of gold and palladium, giving a subtle grey tone. It’s an alternative to white gold that doesn’t require rhodium plating.
• Black gold: Not a natural alloy, but can be created by mixing gold with a black rhodium or ruthenium plating. Some jewellers also achieve a blackened look through controlled oxidation or chemical treatments. For example, a gold-cobalt alloy consists of 75% gold with 25% cobalt and forms a black oxide layer after heat treatment. An olive-tinted hue can also be achieved with a gold-cobalt-chromium alloy (75% gold, 15% cobalt, 10% chromium).

Gold alloys comparison chart

The chart below details the different types of gold alloys, their compositions, purity, and how different metals influence their colour.

GOLD COLOUR	CARAT	FINENESS	GOLD CONTENT	SILVER CONTENT	COPPER CONTENT	OTHER METALS
YELLOW GOLD	22ct	916	91.6%	5%	2%	Zinc (1.33%)
YELLOW GOLD	18ct	750	75%	10%	15%	0%
YELLOW GOLD	18ct	750	75%	15%	10%	0%
YELLOW GOLD	14ct	585	58.3%	30%	11.7%	0%
YELLOW GOLD	10 ct	417	41.7%	52%	6.3%	0%
YELLOW GOLD	9ct	375	42.5%	20%	0%	0%
WHITE GOLD	18ct	750	75%	0%	0%	Platinum or palladium (25%)
WHITE GOLD	18ct	750	75%	0%	0%	Zinc (5%) Palladium (10%) Nickel (10%)
WHITE GOLD	14ct	585	58.3%	32.2%	0%	Palladium (9.5%)
WHITE GOLD	10ct	417	41.7%	47.4%	0%	Palladium (10%) Zinc (0.9%)
WHITE GOLD	9ct	375	37.5%	6.25%	0%	0%
GREY WHITE GOLD	18ct	750	75%	0%	8%	Iron (17%)
ROSE GOLD	18ct	750	75%	2.75%	22.25%	0%
PINK GOLD	18ct	750	75%	5%	20%	0%
RED GOLD	18ct	750	75%	0%	25%	Platinum (10%)
RED GOLD	12ct	500	50%	0%	50%	0%
PURPLE GOLD	19ct	800	80%	0%	0%	Aluminium (20%)
BLUE GOLD	18ct	750	75%	0%	0%	Iron (25%)
DEEP GREEN GOLD	18ct	750	75%	15%	6%	Cadmium (4%)
GREEN GOLD	18ct	750	75%	20%	5%	0%
SOFT GREEN GOLD	18ct	750	75%	25%	0%	0%
LIGHT GREEN GOLD	18ct	750	75%	0%	23%	Cadmium (2%)

Gold alloys in coins

Besides jewellery, gold alloys are frequently used in coinage. Before the 1930s, gold was commonly used in circulating currency. Because pure gold is soft and prone to wear, these coins were minted using gold alloys to help them withstand years of daily transactions. These historical coins are highly sought after by collectors today, but gold is no longer used for circulating coinage like it once was.

In modern times, gold alloys are often used to produce gold bullion coins, which serve as investment assets rather than being used in daily transactions. Many gold bullion coins carry a legal tender face value, but their true worth is determined by their gold content. Knowing the alloy used in a gold bullion coin can help investors understand the real value of their coins according to gold’s current market price.

Some bullion coins, like the Gold Britannia and Canadian Gold Maple Leaf, are minted in pure 24-karat gold (999.9 fineness). Others continue the tradition of gold alloy coinage. These alloyed gold coins still contain exactly one troy ounce (31.10g) of gold, but weigh more due to the additional metals mixed in for strength.

Keep Reading: What are the Best Gold Coins to Buy and Why? From Kruggerands to Maple Leafs

Notable gold alloys in the bullion coin world include:

South African Krugerrand (22-carat, 91.67% gold)

Introduced in 1967, the Gold Krugerrand was the first modern gold bullion coin. It’s minted from 22-carat (916.7 fineness) gold, alloyed with copper. This gives these coins a distinctive reddish hue and increased durability compared to pure gold coins. In fact, the Krugerrand is one of the most durable gold coins available, resistant to scratches and able to withstand handling without being damaged.

American Gold Eagle (22-carat, 91.67% gold)

The U.S. Mint’s flagship bullion coin, the American Gold Eagle, is also minted in 22-carat gold. But unlike the Krugerrand, it contains a mix of silver (3%) and copper (5.33%), giving it a slightly lighter golden hue while still maintaining strength and wear resistance.

British Gold Sovereign (22-carat, 91.67% gold)

The Gold Sovereign is one of the world’s most famous historic gold coins, first issued in 1817. It continues to be minted in 22-carat gold with a copper alloy, making it durable and widely recognised for its slightly reddish hue.

Austrian Gold Ducat (23.75-carat gold, 98.6% gold)

The Austrian Gold Ducat, historically used in Europe, contains an unusual gold purity of 98.6% (23.75-carat), just shy of being pure 24-carat gold. These coins were once circulated, however they’re mostly minted as commemorative pieces for investors today.

Invest in high-quality gold bullion coins

If you’re interested in gold, you might like to view our collection of investment-grade gold bullion coins from the most recognized mints in the world. We stock a range of pure, 24-carat gold coins, including the Vienna Gold Philharmonic and Gold Kangaroo, as well as famous gold alloys like the Gold Krugerrand and British Gold Sovereign. Browse our collection and start investing in gold today.