A
diamond
(from the ancient
Greek
αδ?μα? ? adamas "unbreakable") is a re-arrangement of
carbon
atoms (those are called
allotropes
).
Diamonds have the highest
hardness
of any bulk (all one type) material. Because of this, many important
industries
use diamonds as tools for cutting and polishing things. Many of them are clear, but some of them have colors, like yellow, red, blue, green and pink. Diamonds of a different color are called "fancies".
Big diamonds are very
rare
, and are worth a lot of money. Only 20% of diamonds are fit for jewellery. The other 80% are of lower quality. Those lower quality diamonds are called industrial diamonds, and are used to make things like drill bits and diamond saws. Even if a diamond is not of gem quality, it still has a value because It is very hard.
Cut and faceted diamonds can be attractive hence their use in
jewellery
. Diamonds are very effective
electrical insulators
, but also very good
conductors
of heat. On
Mohs scale of mineral hardness
, diamonds are scored as 10 (the highest score possible).
There are natural and
synthetic
diamonds. The
Earth
makes natural diamonds, and people make synthetic diamonds. Diamonds are the hardest natural substance known to man. Diamonds are made of pure
carbon
, the same
chemical element
as
graphite
,
fullerene
, and
coal
. But diamonds are very hard and in
crystalline
form. It is commonly believed that diamonds are formed from coal, but this is not true.
Diamonds are made deep in the Earth where there is an intense amount of pressure and heat. The formation of natural diamonds needs specific conditions. These are exposure of carbon-bearing materials to high pressure, between 45 and 60
kilobars
(4.5 and 6
GPa
), but at a comparatively low temperature, between about 900 and 1,300 °C (1,650 and 2,370 °F). These conditions are found in two places on Earth: in the
lithospheric mantle
below relatively stable
continental plates
, and at the site of a
meteorite
strike.
[3]
People find diamonds where volcanoes were a long time ago. They sometimes find tiny ones at the site of a
meteorite
strike. Sometimes people find diamonds on the top of the ground. But in places like
South Africa
, they must dig deep down into a diamond
mine
to get diamonds. Diamonds were first found in
India
.
Small synthetic diamonds are made for
abrasive
s. Large synthetic ones are even more expensive to make than to find and dig up, so people don't make large synthetic diamonds.
For many decades the trading of diamonds was controlled by the
De Beers
group of companies, who controlled most of Africa's rich diamond mines. However, in the late 1980s and early 1990s, new diamond mines opened in
Canada
and
Australia
that De Beers wasn't able to control. When the
USSR
collapsed in 1991, many cheap Russian diamonds entered the market, overwhelming De Beers and their efforts to control it. De Beers still runs most of Africa's diamond mines, but their mines now only produce about one third of the world's diamonds.
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