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寶石知識 - 18K金、24K金差在哪?

數字又代表什麼?K 金首飾全解析

Gemstone Knowledge - What's the Difference Between 18K Gold and 24K Gold?

What do the numbers represent? A Complete Analysis of Karat Gold Jewelry

If you've had contact with jewelry, you've probably heard of various types of K gold such as 24K, 18K, 14K, 9K, and so on.
What do these numbers mean exactly?

Gold & Karat Gold

1 Karat Gold equals 1/24, which is 4.17% pure gold. By extension, 14K contains 58.3% pure gold, which can be understood as 14/24 being pure gold, with the remaining 10/24 being other alloys. Similarly, 18K contains 75% pure gold, understood as 18/24 being pure gold, with the remaining 6/24 being other alloys.

Unit of Measurement for Gold

In Taiwan, the common unit of gold weight is "taiqian," while in China and Japan, grams (Gram) are frequently used. In Europe and America, ounces (oz) are common.

1 taiqian = 3.75 grams

1 taiqian = 0.1 liang

1 ounce = 8.2944 taiqian = 31.1035 grams

Why are there different types of K gold, and what are the common types?

As explained earlier, the relationship between K gold and gold content is straightforward: the lower the K number, the lower the gold content.

Pure gold (24K or 999 Gold) is very soft and easily deformable, making it challenging to craft jewellery with. To enhance its hardness and durability, craftsmen historically added small amounts of metals like silver, copper, or zinc to pure gold. This alloying process allows for more refined and durable jewellery.

For example, 18K gold consists of 75% gold and 25% silver and copper. Depending on the proportion of silver and copper, different tones of 18K gold can be produced.

Common types of K gold, based on alloy ratios, include:

  • 24K: Pure gold, comprising 99% gold
  • 18K: 75% gold
  • 14K: 58.5% gold
  • 10K: 41.7% gold
  • 9K: 37.5% gold

Different countries have varying conventions for indicating the gold content in jewellery. In Taiwan, for instance, common inscriptions include 750 for 18K, 585 for 14K, and 375 for 9K. In Japan, it's customary to directly mark jewellery with 9K, 14K, or 18K.

1. 14K、18K、24K Gold Characteristics

18K Gold is also the most commonly used Karat gold in jewellery making.

The primary reason for this is that, compared to pure gold, 18K gold has higher hardness. Additionally, with different proportions of alloy components, it can produce various tones such as yellow, white, or rose, commonly referred to as 18K yellow gold, 18K white gold, and 18K rose gold.

Common Karat gold colors include:

【 Yellow Gold 】: A yellow precious metal alloy composed of gold, copper, and silver.

【 White Gold 】: A white precious metal alloy made by adding palladium, silver, and other elements to gold.

【 Rose Gold 】: A red precious metal alloy created by mixing gold with copper and silver.

▎Common Designs in 14K Gold Jewellery

The principle of 14K gold is similar to that of 18K gold, with the gold content reduced to 58.5%. It has a lower gold content but higher hardness compared to 18K gold. While 14K gold is harder, its lower gold content means it's not as valuable as 18K gold. Therefore, it's more suitable for crafting designer jewellery or pieces with intricate designs.

▎24K Pure Gold Jewellery as a Hedge Investment

24K pure gold is very soft, making it prone to damage and stone loss when setting precious gemstones. Due to its softness, it's also difficult to shape and mold into intricate jewellery designs compared to Karat gold jewelry.

However, pure gold is highly liquid, almost equivalent to currency, and can be easily converted into cash at any time. Therefore, besides being worn for aesthetics, gold jewelry is often purchased from an investment or asset preservation perspective.

Overall, while 18K or 14K gold is better suited for crafting intricate jewellery, in terms of the metal itself, they don't hold value as well as 24K gold. Yet, for aesthetics and durability, 14K or 18K gold remains the better choice.

2. Other Common Precious Metals

▎3D Hard Gold

In addition to the aforementioned Karat gold types, there is a relatively new alloy technology called 3D hard gold. Like 24K gold, it is also 999 pure gold, but the hardness of 3D hard gold is four times that of regular pure gold.

Manufactured using a special process, 3D hard gold involves breaking down the ionic structure of gold during production to increase its hardness. 3D hard gold is also lighter in weight and allows for more versatile designs. However, it comes at a higher price due to the high manufacturing cost, and its value retention is not as good as pure gold, mainly used for jewellery wear.


Platinum (PT), also known as white gold or pure white gold, is a naturally occurring single precious metal with a silver-white color. It is highly resistant to high temperatures and strong acids and bases and is less prone to oxidation. Platinum has a higher density than gold, meaning an equal volume of platinum will weigh more than Karat gold.

Platinum is rare in nature compared to gold, and its high melting point makes refining platinum more difficult, resulting in higher losses. Due to its high density and hardness, crafting platinum requires higher levels of craftsmanship than gold, making it a precious metal.

Internationally, the purity of platinum is marked with symbols such as PT, Plat, or Platinum, followed by the purity percentage. For example, Pt950 indicates a purity of 95%. The Platinum Guild International (PGI) stipulates that PT850 and above can be called platinum. Specifications for platinum jewellery include PT950, PT900, and PT850.

PT950: Platinum is 95%, palladium is 5%. PT900: Platinum is 90%, palladium is 10%. PT850: Platinum is 85%, palladium, and copper are 15%. Platinum's major advantage lies in its high hardness and original silver-white color, making it ideal for highlighting the brilliance of white diamonds, commonly used in diamond ring designs.

▎Low Karat Alloys like 9K and 10K

Fans of Japanese-style lightweight jewellery often come across K gold engravings such as 9K and 10K in their jewellery pieces. Despite the lower gold content, these K gold alloys offer benefits such as color retention and durability compared to jewelry prone to fading or oxidation.

Therefore, they are favored by lightweight jewelry brands that prioritize aesthetics and can also be found in antique jewellery pieces.

3. K Gold Products in OYJ

In OYJ's creative jewellery line, besides integrating various cultural elements into the designs, there's a strong emphasis on the importance of everyday wearability. The aim is for everyone to find jewelry suitable for different aspects of themselves across the various collections.

Jewellery designed for frequent wear must retain its color and durability.

With the recent increase in hand washing frequency, many electroplated jewellery pieces may struggle to withstand frequent contact with alcohol or extensive water exposure. That's why, for the Spring/Summer 2021 season, OYJ has introduced the Pure 18K Gold Haute Provence collection. This collection reinterprets the classic Provence series using pure 18K gold and diamonds.

OYJ recommends 18K gold pieces.

18K gold jewellery

    For more inquiries about loose stones and K gold jewelry customization, you can schedule an appointment with the jewellery consultants at Olivia Yao Fine Jewellery Salon!

    Editor | Olivia

    珠寶設計師 / 品牌創辦人 / 會計師 / 旅遊狂熱者,有著不安於室的反骨靈魂,把自小的興趣變成終身職業,從會計師轉換跑道變成珠寶設計師,成立自己的同名品牌,用輕珠寶打動女性的心,現在在全球已經有超過 20 個國際通路可以看到 OLIVIA YAO JEWELLERY,也讓每位有夢想的女性看到更多生活方式的可能。