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ImageThey can cut metal. They can cut glass. They are billions of years old and form deep within Earth. Some are so rare and beautiful that people will pay a fortune to get one! They are diamonds.


Diamonds are made of carbon, a chemical element. That’s the same stuff that’s in the tip of a pencil. But isn’t carbon soft, not hard?

Pencil carbon is so soft that it rubs off on paper. But diamond carbon is so hard it can cut almost anything. In fact, diamonds are the hardest things in nature. What makes the difference? The atoms inside a diamond have a special crystal shape. This makes them very hard.

Some diamonds can sparkle brilliantly. Such diamonds are rare. They are precious and valuable, and people wear them as jewelry. But most diamonds are small and contain flaws. These are worth much less.


Big diamonds form deep under the ground. The heat and pressure at great depths melts carbon-rich rocks. Diamonds form out of this molten (melted) rock. The diamonds are later brought to Earth’s surface by currents of molten rock. The entire process can take billions of years!

Smaller diamonds can form closer to Earth’s surface. Movements of the planet’s crust lift these stones up from the depths.


You can scratch or cut just about anything with a diamond—except another diamond. On a scale of hardness from 1 to 10 with 10 as the hardest, diamonds are a 10.

Because they are so hard, diamonds are great for drills, saws, and other cutting tools. That makes them very useful in mining and manufacturing.


Are there any shortcuts to making diamonds? Actually, there are. People have learned how to make artificial diamonds and other gems. Diamonds made by people are called synthetic diamonds.

Synthetic diamonds look and act like the real thing. They’re as hard as natural ones. In fact, most diamonds used for industrial purposes are synthetic.

Imitation diamonds aren’t diamonds at all. They’re usually made from inexpensive materials that sparkle brightly, such as quartz or glass. But they aren’t as hard as natural or synthetic diamonds. Imitation diamonds are used mostly in jewelry.


Diamonds found in the ground are rough. They don’t shine like the gems in jewelry stores. They look greasy or dirty. So how do you make diamonds really sparkle? You cut them.

Cutting a diamond gives the stone edges that bring out the shine. Diamond cutters trim away flaws such as cracks or cloudy spots.

It takes careful planning to cut a diamond. The goal is to make the diamond as large and as valuable as possible. Even so, a cutter slices away about half of a diamond’s original size. After polishing, the cut diamond is ready to sell.


Diamonds are judged by the “4 Cs.” These are color, clarity, carat weight, and cut.

Color: When diamonds form, small amounts of minerals get inside them. This changes their color. Colorless stones are very desirable. Yellowish or brownish ones are not.

Clarity: Can you see flaws in the diamond? A diamond with great clarity has no visible flaws. The clearer a stone is, the greater its value.

Carat weight: The heavier a diamond is, the better. Because large, heavy diamonds are less common, they are more valuable. A diamond that weighs 2 carats or more is usually considered large.

Cut: Diamond cutters decide on the shape and proportion of a stone. An attractive cut makes a diamond more desirable.


The largest natural diamond ever found is the famous Cullinan diamond. It was discovered in South Africa in 1905. The Cullinan tipped the scales at an amazing 3,106 carats!

What do you do with a diamond that big? The Cullinan was cut into 105 different gems. The largest of these is called the Star of Africa. It is the largest cut diamond in the world. Today, the Star of Africa sits on the end of the British royal scepter.

Source: Microsoft ® Encarta