Diamond is the birthstone for April. It is also the most popular gemstone in the world. This wasn't always the case. Diamonds used to be sought after by only the very wealthy and powerful. They were much too rare and valuable to be owned by the average person. This changed in the mid to late 1800's when diamond deposits were found in South Africa. The marketing campaign "A diamond is forever" by De Beers forever changed the landscape of the gemstone world, making diamonds the most desirable gemstone.
When most people think of diamonds, they think of colorless. Diamonds come in many colors, however. Yellow and Brown are the most common of the colored diamonds. Much rarer and much more valuable types include blue, pink, purple, orange, green, and red. Some diamonds can be irradiated to give them colors, many of these are much more vibrant that a natural colored stone, and much more common. The procedure is safe and does not leave any lasting radiation.
Diamonds are made of carbon, the only gemstone to made of a single element. Yellow diamonds are colored by trace elements of nitrogen, and blue diamonds are colored by trace elements of boron. Diamond, at a 10 on the Moh's scale of hardness, is the hardness gemstone in the world. Only a diamond can scratch a diamond, but a hard hit can chip one.