Based on the provided reference, the fineness number 666 corresponds to 16 karat gold.
Understanding gold purity is essential whether you are buying or selling jewelry or other gold items. Gold purity is typically measured in karats or fineness. While karat indicates the proportion of pure gold out of 24 parts, fineness uses a three-digit number to show the parts per thousand of pure gold in an alloy.
Gold Purity Conversion
The fineness number 666 signifies that the metal alloy contains 666 parts of pure gold out of 1000 parts. This is a common way to express gold purity, especially in some countries.
According to the Gold Purity Conversion Chart from the reference:
| Number of Karats | Parts of Gold | Fineness |
|---|---|---|
| 16k | 16/24 | 666 |
| 17k | 17/24 | 708 |
| 18k | 18/24 | 750 |
| 19k | 19/24 | 791 |
As shown in the table, the fineness mark '666' directly correlates with 16 karat (16k) gold. This means 16 parts of the metal are pure gold, and 8 parts are other metals (like copper, silver, or zinc) to provide strength and durability.
Karat vs. Fineness
- Karat (k): Represents the proportion of pure gold out of 24 parts. 24k is pure gold (24/24).
- Fineness: Represents the proportion of pure gold out of 1000 parts. Pure gold is 1000 fineness (or 999.9 for practical purposes).
To convert fineness to karats, you can use the formula: Karat = (Fineness / 1000) * 24.
For 666 fineness: (666 / 1000) * 24 = 0.666 * 24 ≈ 15.984, which rounds to 16 karats.
Conversely, to convert karats to fineness: Fineness = (Karat / 24) * 1000.
For 16 karats: (16 / 24) * 1000 ≈ 0.6666... * 1000 ≈ 666.
Understanding these markings helps in identifying the actual gold content in an item.
