Opals and emeralds
Opal is one of the most fascinating gems in the world thanks to its changing colours. The mineral is made of hydrated silica (SiO2.nH2O, this means that the mineral structure also includes water molecules) and it is shapeless. The most appreciated varieties are: noble opal, milky and with vivacious iridescence, harlequin opal, and fire opal, which is more transparent than noble opal and has a bright orange colour.
The turquoise variety has a cerulean colour and looks like porcelain. The most beautiful examples come from Iran, while the American turquoise variety is less valuable since it is more degradable.
The name emerald comes from the Greek “smaragdos“, which means green stone. The most ancient deposits, exploited by Pharaohes, were located on the Egyptian coast of the Red Sea. At the moment, most of the production comes from Columbia, Brazil and the Ural Mountains. The green colour of emeralds is due to the presence of vanadium and chromium oxide.
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Magnets and superconductors
Which one of us has not played at attracting small pieces of iron with a magnet?
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13 May 2013
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Have you ever wondered how much space is taken up by an apple or a steak?...
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18 January 2016
Ten years of oil demand
Eni has recently published the 14th edition of the 2015 World Oil and Gas Review...
28 August 2020
The Earth seen from above: signs of fires
This image was taken by the ASTER sensor installed on the NASA TERRA satellite platform. The image was taken on…
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8 November 2013
Magnets and superconductors
Which one of us has not played at attracting small pieces of iron with a magnet?
From the Multimedia section
Facts
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Mountains on the Earth
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And in underground tunnels?
There are groups of terrestrial animals that eat insects, worms and other invertebrates...
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13 May 2011
Volcanic eruptions
The activity of some volcanoes is characterized by violent explosions...
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Volcanic activity of Vesuvio
One of the most famous volcanic disasters was the eruption of Vesuvio in 79 A.D....