For instance, diamonds repel water, but readily accept grease. This bit of information may not be exciting to you, but these properties are used in diamond mining to help separate diamonds from gravel.

Most people are aware of diamond's hardness, but may not know that diamond is probably hundreds of times harder than other gems. It's difficult for science to measure exactly how hard diamond is, because there is no harder substance to measure diamond against.

Diamond, unlike other gems, can be composed of just carbon... but a few atoms of other elements such as nitrogen and boron can find their way into a diamond's structure. These trace elements in a diamond can cause colored diamonds.

In fact, diamonds occur in many colors including shades of blue, green, red, orange, yellow, brown, and black. So if your birthstone is diamond and you prefer one with color, you're in luck.

But most diamonds are near colorless. These diamonds derive their beauty from their brilliance, luster, and dispersion (breaking up light into a rainbow of colors).

Oh, one more little oddity about diamond being made of carbon... it's the only gem I can think of that can be made of a single element.

Those little things inside most diamonds aren't carbon spots, They're properly referred to as inclusions, and are usually tiny crystals of other minerals such as other diamond crystals or garnet. Other types of inclusions can also occur that we don't have space to discuss here today.

Some diamonds glow in the dark when illuminated by ultraviolet light. A few diamonds can even absorb the high-energy radiation of the ultraviolet light, and re-emit it as visible light. These diamonds are called fluorescent. Some can even continue glowing after the ultraviolet source is turned off. These diamonds are known as phosphorescent.

I hope that I gave you some new and interesting information about the April birthstone.

To answer that other question... diamonds are relatively expensive. Like other gems, the cost relates directly to quality and size (those 4 C's). Small commercial grade diamonds can sell for several hundred dollars per carat. Larger diamonds can sell for many thousands per carat. A few large diamonds with famous former owners have sold for more than a million dollars.

Diamonds of all grades and sizes are readily available, from a round, single cut, TLB, one pointer, on up to gems like the oval shaped $34,000 beauty pictured here..

 Now, let me tell you what some of the above terminology really means:

• Round is the diamond's shape (you knew that)
• Single cut means it has seventeen facets rather than a full cut's fifty eight facets
• TLB is a color designation, meaning Top Light Brown
• One pointer means a weight of 1/100 of a carat

Diamond, the April birthstone is by far the most popular gem stone, and April babies are happy with their birthstone.