The typical engagement ring diamond in the United States weighs between 1.08 and 1.2 carats. However, as previously said, there are other aspects other than a diamond's carat weight that influence how magnificent and attractive it appears in an engagement ring. Color is one of them. Even though colorless diamonds are the most valuable, they are not available in enough quantities to account for more than a small fraction of all diamonds. The other major type of diamond is called "white", which is actually just another name for unpolished diamond. Black diamonds occur naturally in some places like South Africa but they are rare. Blue diamonds also occur naturally but they are even more rare. Gold or silver colored diamonds can be created by treating the diamond with acids or salts. Red diamonds result from exposure to radiation such as that found in deep space. Pink diamonds can result from exposure to radiation or elements within the earth's atmosphere such as sulfur dioxide gas. Brown diamonds appear dark gray or brown due to carbonaceous (organic) material that has been deposited inside the stone during its formation deep within the earth's crust, similar to how coal forms inside fossils. Even though black, blue, gold, silver, pink, red, or brown diamonds may exist, they are very rare. People usually want white diamonds because they think that any other color is going to make the ring look cheap.