Understanding the Softness of Pure Gold and Its Applications

Gold is one of the most precious metals known to humans, and its unique properties have fascinated people for centuries. One of the most notable characteristics of gold is its softness, which has shaped its uses and applications in various industries. In this article, we will explore the softness of pure gold, its hardness on the Mohs scale, and why it is often alloyed with other metals to improve its durability.

The Softness of Pure Gold

Pure gold, also known as 24-karat gold, is a naturally soft and malleable metal. On the Mohs scale of mineral hardness, which measures the scratch resistance of different materials, pure gold has a hardness of approximately 2.5 to 3. This makes it extremely susceptible to scratching, which is why it is rarely used alone in jewelry or other applications.

Alloying Gold to Increase its Durability

Due to its softness, pure gold is often alloyed with other metals to enhance its durability and strength. Common metals used in alloying include copper, silver, and sometimes platinum. These metals, when added to gold, increase its hardness, making it more suitable for everyday use and compatible with various manufacturing processes.

Common Misconceptions About Pure Gold

It is a common misconception that 24-karat gold is 100% pure or that pure gold exists in its pure form in everyday jewelry items. While 24-karat gold is the purest form of gold, it is not commonly used for making jewelry because of its softness. Instead, gold is often alloyed to create different karat grades that are more suitable for jewelry and other applications.

Karat Grading of Gold

Gold is available in different karat grades, each with a different percentage of pure gold. Here are the most common ones:

24-karat gold: This is the purest form of gold, containing 99.99% pure gold. It is too soft to be used in jewelry and is typically found in the form of coins, bars, and biscuits. 22-karat gold: This is the most common karat grade for jewelry, as it contains 91.67% pure gold. The addition of other metals strengthens the gold, making it easier to mold into intricate designs and hold its shape. 18-karat gold: This grade contains 75% pure gold and is widely used in jewelry and other applications. It is a good balance between purity and durability. 14-karat gold: This grade contains 58.33% pure gold and is less pure but still retains many of the properties of pure gold, making it a popular choice for affordable jewelry.

Physical Properties of Gold vs Other Metals

For a comparison, we can look at some physical properties of gold, lead, and iron:

Lead Gold Iron Young's Modulus (GPa) 16 79 211 Mohs Hardness 2.5 2.5 4 Vickers Hardness (MPa) 188-216 608 Brinell Hardness (MPa) 38-50 188-245 200-480

While pure gold is softer than iron but harder than lead, these physical properties play a crucial role in determining the suitability of gold for different applications.

As a final note, while 24-karat gold is the purest form of gold, it is rarely used in jewelry due to its softness. Instead, alloys such as 22-karat, 18-karat, and 14-karat are more commonly used, as they provide a balance between purity and durability, making them ideal for everyday wear and use.

For more detailed information on the varieties and uses of gold, we encourage you to read the full explanation available here!