Gold purity explained
Gold purity is measured in karats.
The karat (US spelling, symbol K or kt) or carat (UK spelling, symbol C or ct is a fractional measure of purity for gold alloys, in parts fine per 24 parts whole. The karat system is a standard adopted by US federal law
24-karat gold is pure (while 100% purity is unattainable, this designation is permitted in commerce for 99.95% purity), 18-karat gold is 18 parts gold, 6 parts another metal (forming an alloy with 75% gold), 12-karat gold is 12 parts gold (12 parts another metal), and so forth.[18]
In England, the carat was divisible into four grains, and the grain was divisible into four quarts. For example, a gold alloy of 127⁄128 fineness (that is, 99.2% purity) could have been described as being 23-karat, 3-grain, 1-quart gold.
The karat fractional system is increasingly being complemented or superseded by the millesimal system, described above.
Conversion between percentage of pure gold and karats:
- 58.33–62.50% = 14K (acclaimed 58.33%)
- 75.00–79.16% = 18K (acclaimed 75.00%)
- 91.66–95.83% = 22K (acclaimed 91.66%)
- 95.83–99.95% = 23K (acclaimed 95.83%)
- 99.95–100% = 24K (acclaimed 99.95%)