Gold Karat and its weight

A friend of mine emailed me asking for the purity of 10k rose gold. This is the informaion I have given to him.
Gold Karat: (in UK it spells carat)
1k    .0417
2k    .0833
3k    .1250
4k    .1667
5k    .2083
6k    .2500
7k    .2910
8k    .3333
9k    .3750
10k  .4167
11k  .4583
12k  .5000
13k  .5417
14k  .5833
15k  .6250
16k  .6667
17k  .7083
18k  .7500
19k  .7910
20k  .8333
21k  .8750
22k  .9167
23k  .9583
24k  1.000
Letters in red mean most commonly produced in jewelry.
Fine (pure) gold is too soft for jewelry, thus we have to mix with alloy to achieve a desired hardness. Silver and copper are the two common components, but many others can be used.

Thus, The proportion amount of 10k gold is .4167% pure gold and .5833% for alloy
By law, a metal described as 10k must be at least .4167 gold. The remainder of the alloy is not really stricted by law.

In jewelry market, we have 3 colors of gold jewelry, yellow, white and pink (rose gold).
By using specific alloy the metal can change to the desired color. Just check with your local alloy suppliers

Gold Karat weighs differently, the chart below will give you some ideas

After sending the above, I expected my friend would give me a big thank, but he just said the information was too long and irrelevant!!