The gold stamp 10K means that the gold is 41.7% pure gold and 58.3% other alloys such as copper, silver and nickel. These alloys are mixed in with the pure 24K gold to strengthen it, as 24K is considered too soft for every day wear and will bend and scratch easily. 10K gold is the lowest purity that can legally be called gold in the US, however it is a beautiful and durable alternative to more expensive 14K and 18K gold jewelry. The higher content of other alloys like silver strengthen 10K gold so that it is the hardest of all the gold types and will resist scratching longer than both 14K and 18K (but it will still scratch- all metals scratch when in contact with an abrasive surface).
10K gold will be somewhat paler in color than both 14K and 18K. Pure 24K gold is often considered too saturated or “orangey” in color, so mixing it will alloys also makes the color more attractive to the average person. If it is 10K white gold, keep in mind that you will need to rhodium plate your ring once a year to once every 2 years to retain that icy white color. Rhodium plating is a white metal plating that is used to boost the white color of 10k, 14k and 18k white gold rings; rhodium plating is considered standard practice amongst jewelers.
Below are all the standard gold alloy karat marks that you should be able to find on any item of fine jewelry. The US marks us the ‘K’ to denote karat; UK and European jewelry will often feature the gold’s purity percentage to describe the karat. However, due to the internet, jewelry is often sourced from all over the world, seeing the numerical percentage rate inscribed on the inside of a ring or on a piece of jewelry will become more and more common.
24K = .999
18K = .750
14K = .585
10K = .417
Here is a picture of the various gold colors by karat
Jewelry Industry Professional for 14 Years, Adiamor.com