Common jewelry metals (18K, PT950, S925)

Jewelry is mainly composed of two parts: gemstone and metal. Never underestimate the importance of jewelry metal after you have chosen the gemstone of your liking.

Metals of poor quality could oxidize and discolor easily, which could cause the whole jewelry to lose its shine. Metals which are too soft could deform easily and are not secure enough for gemstone mounting, which means gemstone could fell off often.

This article aims to introduce three kinds of most common jewelry metals: 18K gold, platinum and sterling silver.




18K Gold (AU750)

18K gold is when the metal structure of 100% pure gold is divided into 24 parts and 18 of them are pure gold. In other words, this means 75% of the gold and thus the metal code for this is AU750. There are also other K golds in the market, namely 14K (58.5% pure gold / AU585) and 9K (37.5% pure gold / AU375). Gold of lower purity has lower resistance against oxidization.

There are mainly three types of color for 18K gold, which are white (white gold), brown copper (rose gold) and yellow (yellow gold). They are all composed of 75% pure gold and 25% other metals. The golds gain their respective colors and extra hardness through these combinations.


18K gold is the most common material for jewelries mounted with diamond and other precious gemstones. It is popular for three main reasons:


Merit 1. High hardness

The hardness of 18K gold is higher than that of other rare metals, which means it can protect the gemstone better. High hardness also means it can resist scratches and grinds so the jewelry would not be damaged easily.


Merit 2. Oxidization resistance

18K gold is good when it comes to resisting oxidization and maintaining shine.

Under normal circumstances, the jewelry could be worn for several years and still look 80% new.

Merit 3. High liquidity

Re-selling of 18K goldwares is common.

And if the price of gold rises, it is possible to benefit from the spread from selling out old goldwares.


Demerit 1. Need for maintenance

It is advised that 18K goldwares are to be maintained every few years, depending on how they are worn.




Platinum (PT950)

PT950 is composed of 95% rare metals “platinum” and 5% other metals. This naturally silver-white-color platinum is extremely durable and does not oxidize, which makes it an ideal material for jewelries.

Merit 1. Does not oxidize

Platinum is a metal that does not oxidize, meaning it excels in retaining the shine of jewelry.


Merit 2. High sense of weight

Platinum has a high density so it will give you a “weighty” feel when being worn.

Platinum jewelry would be obviously heavier that 18K gold and sterling silver jewelry.


Merit 3. High liquidity

Re-selling of platinum is also common.

It is possible to benefit from the spread from selling out old platinum jewelries if the platinum’s price rises.


Demerit 1. Average hardness

Platinum is hard enough to protect gemstones but is average when it comes to scratches and grinds protection.

Demerit 2. Being silver-white in color only

Sterling silver (S925)

925 sterling silver is a common silver-white metal, consisting of 92.5% rare metal “silver” and 7.5% other metals. Since 925 sterling silver has lower hardness and oxidization resistance, and could turn dark easily, jewelers would add a coating of other white metal on the surface of sterling silver (sterling silver plated with white gold). However, it still needs to be cleaned regularly in order to keep its shine.

Merit 1. Low price

A piece of sterling silverware would only cost tens to few hundred dollars.

Merit 2. Can be cleaned

While sterling silver requires frequent cleaning, cleaning it is not difficult.


Demerit 1. Too soft

Sterling silver can deform and have scratches easily, and claws made with sterling silver could not grapple gemstones firmly.


Demerit 2. Could oxidize easily

Sterling silver would oxidize and turn dark after being exposed to oxygen.

Even when plated with white gold, its color could only last for six to twelve months.


Demerit 3. Lacking liquidity

The price of sterling silver is only about one-hundredth of that of yellow gold, so it is of no value when it comes to re-selling.



For gemstone-mounted jewelries, the use of metal material plays a critical role as it can affect the look of the jewelry , and in turn how the jewelry is perceived.

This is something that should not be overlooked.