The Arco Valley Pearl is a white natural blister  575-carat baroque pearl.  With pink and yellow overtones the Arco Valley pearl is the second largest pearl in the world second to the 'Pearl of Allah'. The pearl dates back to the 11th century once owned by Chinese, Persian and Mongolian emperors. Mongolian emperor, Khubilai Khan who then reportedly gifted the famous pearl to Marco Polo. The pearl was then handed down to an Austrian Aristocratic family, the Arco Valleys which is who the pearl is named after. 
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The Arco Valley Pearl is white but also shimmers shades of blue and pink. shimmering shades of blue and pink. When the pearl was inspected by pearl specialists, they found that there were holes in the pearl, which suggests that it was once mounted on a tiara or crown. 
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Since the Arco Valleys ownership of the pearl, it wasn't seen again till 2007 where it appeared at an Abu Dhabi auction. The current where abouts of the pearl is currently unknown however is still believed to be somewhere in Europe.
The Arco Valley pearl is valued at $8 million USD. 
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Photo Credit: Unknown author - This photo was taken before 1945 in Germany of Anton Graf von Arco auf Valley.