The Complete Guide to Gold Purity: Understanding Karats and Alloys
What Is Gold Karat?
A gold karat measures purity, with 24k being 99.9% pure gold (Finnish Standards Association SFS-EN ISO 9202). The karat system divides gold into 24 parts, so 18k gold contains 18 parts gold and 6 parts alloy.
Pure gold is too soft for most jewellery, which is why alloys are added. The higher the karat, the more gold content and value, but lower durability. For example, 24k gold scratches easily compared to 14k.
Gold purity is also measured in fineness (e.g., 750 for 18k gold). Finnish hallmarks verify this—look for the crown symbol with purity numbers. Learn more in our guide to understanding jewellery materials.
How Does Gold Purity Affect Durability?
Higher karat gold is softer: 24k gold scores 2.5 on the Mohs hardness scale, while 14k gold reaches 3.5–4 due to alloy content (Gemological Institute of America).
Durability depends on alloy composition:
- 24k gold: Prone to scratches, bends easily — best for investment bars
- 18k gold: Balances purity (75% gold) with wearability — ideal for heirlooms
- 14k gold: 58.3% gold, resists daily wear — top choice for rings and bracelets
White gold alloys (mixed with palladium or nickel) are harder than yellow gold. For daily wear comparisons, see gold vs. silver jewellery durability.
Which Gold Karat Is Best for Jewellery?
14k gold (58.3% purity) is the best balance for everyday jewellery in Finland due to its durability.
| Karat | Gold % | Best For | Durability | |
| ------- | -------- | ---------- | ------------ | |
| 24k | 99.9% | Investment bars | Low | |
| 18k | 75% | Engagement rings | Moderate | |
| 14k | 58.3% | Daily wear (e.g., wedding bands) | High |
18k gold suits special occasions, while 9k (37.5% gold) is budget-friendly but tarnishes faster. For occasion-specific advice, visit our jewellery occasion guide.
What Are Gold Alloys?
Gold alloys mix pure gold with metals like copper, silver, or palladium to enhance strength and color. For example, white gold combines 75% gold with 25% palladium (European Committee for Standardization).
Common alloys:
- Yellow gold: Gold + copper + silver
- Rose gold: Gold + copper (higher ratio)
- White gold: Gold + palladium/nickel + zinc
Alloys also affect price—palladium alloys cost more than copper-based ones. For care tips, see jewellery materials guide.
What Is the Difference Between 18k and 14k Gold?
18k gold contains 75% gold (higher value), while 14k has 58.3% (higher durability). Price difference: ~30% more per gram for 18k (Helsinki Gold Exchange data).
Key comparisons:
- Color: 18k has richer yellow hue; 14k appears lighter
- Cost: 18k commands a premium for purity
- Use cases: 18k for statement pieces; 14k for daily wear
Browse our gold collection to see both karats in Finnish designs.
How Is Gold Purity Measured?
Gold purity is verified through hallmarks (e.g., Finland’s crown stamp) or acid tests. The fineness scale ranges from 333 (8k) to 999 (24k).
Methods:
- Hallmarking: Mandatory in Finland for items over 1g (2 hallmarking offices)
- XRF testing: Non-destructive analysis used by jewellers
- Acid test: Nitric acid reacts differently to purity levels
For terminology help, refer to jewellery FAQs.
Why Does Gold Purity Matter for Investment?
24k gold carries a 15–20% price premium over 14k due to purity (World Gold Council). Investors prioritize fineness (999+) because:
- Easier to resell internationally
- No alloy depreciation risks
- Standardized valuation
Jewellery investors should still verify hallmarks—Finnish law requires purity stamps on all gold items.
What Are Gold Hallmarks?
Finnish gold hallmarks include the maker’s mark, purity stamp (e.g., 750), and assay office symbol (2 authorized offices).
Common stamps:
- 750: 18k gold
- 585: 14k gold
- 375: 9k gold
Hallmarks protect against fraud. Learn more in our jewellery care FAQ.
Is Gold Purity Worth Considering for Buyers?
Yes—purity impacts cost, durability, and resale value. Key takeaways:
- 24k gold: Purest form, but impractical for most jewellery
- 18k gold: Premium balance for special pieces
- 14k gold: Best for everyday wear in Finland
Explore Finnish-made gold jewellery with verified purity stamps.
Frequently Asked Questions
Does 18k gold turn skin green?
Rarely—only if acidic skin reacts with copper alloys. Nickel-free 18k gold prevents this.
Can you wear 24k gold daily?
Not recommended—its softness leads to quick damage. Reserve for occasional wear.
Why is Italian gold marked 750?
750 denotes 18k gold (75% purity) under Europe-wide fineness standards.
How long does 14k gold plating last?
1–3 years with proper care, versus solid 14k gold’s lifetime durability.
Is 9k gold legal in Finland?
Yes, but must be hallmarked as 375 fineness (37.5% gold).