Pay attention to the next star that you will see shine: it could be a big diamond.
Only in 2000, in fact, a group of American astronomers has identified a white dwarf, a dying star, made entirely of diamond!
This big crystal, with the weight of billions of billions of carats, would be formed by the carbon dust from the star crystallized over time.
Although the "white dwarf" is too far away to study its composition, there is substantial evidence that the Milky Way is a real diamond mine!
In 1981, for example, researchers from the Smithsonian Institute in Washington found traces of pure diamond inside a meteorite recovered in Antarctica.
According to scientists, the diamonds could have been formed by the impact of asteroids.
In 1991, however, two Canadian geologists, David Carlisle and Dennis Braman, announced the discovery of a field of tiny diamonds dating back to 65 million years ago.
Exactly the period to which many scientists attribute the impact between the Earth and a huge meteorite that would have caused, among other things, the extinction of the dinosaurs on Earth.

Journey to Earth's mantle
Nature takes millions of years to produce a diamond!
In order to the carbon cristallizes in the form of the most precious stone that is known to the world, are necesarie high pressures produced at depths unreachable land, in the order of 300 km! There the earth's surface pressure can reach 300 thousand atmospheres! At that temperature, which exceeds 2,000 degrees Celsius, the carbon atoms orders themselves in an extremely dense and compact atomic structure.
That's why the diamond is still the strongest material known in nature.
Often the variations of pressure and temperature that the diamonds formed in the Earth's mantle during their ascent to the surface make that the carbon atoms come out from the soil in the form of graphite: the material of which the pencils are made.
"Geologists have discovered vast deposits of graphite ordinaria that once had to be pure diamonds" says Robert M. Hazen in his book "The Diamond Makers".
"In order that the diamond remains that, once reached the Earth's surface, his trip has to be quick and violent, so as to suffer a huge overhang of pressure and temperature", says Hazen.
The fastest journey that matter can experience from the Earth's center to sunlight is an volcanic eruption.
"A mass of diamond can remain undisturbed underground for billions of years,", says Hazen, "but if it is involved in a volcanic eruption, it takes less than an hour to reach the surface".