Solid Gold

[inertia]

If pure gold is 24K then is 12K gold 50% gold? Is this by weight, volume, basic formula or what?

I know white gold has nickel in it, but is "white gold" a specific alloy or is it kinda' fast and loose?

[UrbanChic]

I'm not sure if it's a specific alloy or not, but I wanted to chime in and say white gold alloy can also be made with palladium.

[Duck Duck Goose]

More than you probably wanted to know about the gold alloys known as "white gold".
http://www.18carat.co.uk/whatiswhitegold.html

It's by percentage.
http://jewelry.about.com/library/glossary/bldef_karat.htm
24 karat (24K) gold is pure gold.

18 karat (18K) gold contains 18 parts gold and 6 parts another metal or metals, making it 75% gold.

14 karat (14K) gold contains 14 parts gold and 10 parts another metal or metals, making it 58.3% gold.

10 karat (10K) gold contains 10 parts gold and 14 parts another metal or metals, making it 41.7% gold. 10k gold is the minimum karat designation that can still be called gold in the US.
http://co-trading-post.com/tp_html/metal.htm
Gold quality is measured in units call karats. Karats refer to the fractional parts of pure gold in the total alloy. Pure gold is 24K. The quality expression is always in karats: such as 10K, 12K, 14K or 18K. This literally means 10/24ths, 12/24ths, 14/24ths or 18/24ths fractional parts of gold. The resulting numbers are 42% fine gold in 10K gold, 50% fine gold in 12K gold, 58% fine gold in 14K gold and 75% fine gold in 18K gold. So yeah, a 12K gold toe ring would be 50% gold.

[samclem]

While all of the above is correct, I would suggest that If you see a ring or item marked "12K" you should also pay attention to an additional markings(which are quite often "G.F."). This means that the ring is gold filled.

Basically, in the US, they don't make things out of 12 K gold. Also if the "12K" is preceeded by a fraction such as 1/20 or 1/10, this also indicates gold filled.