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.
Special reports
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Which one of us has not played at attracting small pieces of iron with a magnet?
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Urban woods
When walking along a tree-lined avenue in a crowded and traffic-congested city, wrapped up in our daily commitments, we do…
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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?
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6 September 2009
Oil fields beneath the ice
Con la graduale scomparsa del ghiaccio marino in seguito al...
13 May 2013
Small steps, great footprints
Have you ever wondered how much space is taken up by an apple or a steak?...
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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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Volcanic activity of Vesuvio
One of the most famous volcanic disasters was the eruption of Vesuvio in 79 A.D....
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Mountains on the Earth
The different landscapes that we analysed in the previous section are distributed...
And in underground tunnels?
There are groups of terrestrial animals that eat insects, worms and other invertebrates...
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An artificial geyser
Electric and thermal power produced from geothermal energy depend on the existence of underground infiltrations...
Laterite and bauxite deposits
These deposits can be observed in those tropical areas that are characterized by...
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13 May 2011
Volcanic eruptions
The activity of some volcanoes is characterized by violent explosions...
Volcanic activity of Vesuvio
One of the most famous volcanic disasters was the eruption of Vesuvio in 79 A.D....
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Mountains on the Earth
The different landscapes that we analysed in the previous section are distributed...
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24 February 2011
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....