Rink
06-11-2004, 04:50 AM
Posted on Wed, Jun. 09, 2004
<font size=4>Zircons worth more than diamonds for scientists</font>
By ROBERT S. BOYD
Knight Ridder Newspapers
WASHINGTON - Zircons: To lovers on a budget, they're low-cost jewelry. But to scientists, they're more precious than diamonds.
That's because they're the most ancient materials on Earth, guarding within their crystal depths an unequaled record of the infancy of our planet.
"The oldest dates we know about on Earth come from zircons," said John Hanchar, a geologist at George Washington University in Washington.
A fragment of zircon only a few thousands of an inch across that was picked up in the Jack Hills region of western Australia holds the record age of 4.404 billion years.
"Earth itself had formed less than 150 million years earlier," said Edmond Mathez, a geologist and zircon expert at the American Museum of Natural History in New York.
An even more archaic zircon, of extraterrestrial origin, was found in the remains of a 6-ton meteorite known as Vaca Muerta (Dead Cow) in the Atacama Desert of Chile. The gem was forged at least 4.6 billion years ago in the swirling disk of dust and rocks surrounding the sun that gave birth to the planets.
"It's the oldest thing ever dated in the solar system," Hanchar said.
Mathez called zircon "a unique clock (and) one of the most important tools geologists have for studying the long distant past."
Zircons have been used, for example, to date the assembly and movement of continents across the face of the Earth, according to a report by Richard Hanson, a geologist at Texas Christian University in Fort Worth, in the May 21 issue of Science.
A zircon crystal consists of the elements zirconium, silicon and oxygen. In nature it's yellow, gold or brown, but when heated turns a dazzling blue. The name comes from the Persian "zargun," meaning "gold color."
Zircons, incidentally, aren't the same chemically as "cubic zirconia," though both are used as cheap substitutes for diamonds in jewelry. Cubic zircon is a compound of zirconium, oxygen and, usually, yttrium, discovered in 1937. It lacks the silicon that's in a true zircon, and is, of course, very much younger.
According to the Complete Jewish Bible, zircon was one of 12 gemstones that Moses ordered put on a breastplate for his brother, Aaron, as described in the book of Exodus, 28:19 and 39:12. (Other biblical translations call the stone "ligure" instead of zircon. It's also known as jargon, hyacinth or jacinth.)
Geologists prize zircon for its durability. It remains unscathed while other rocks and minerals melt and are re-formed under the tremendous heat and pressure of continental shifts, mountain-building and the violent asteroid impacts of the hellish "Hadean" epoch during Earth's first 700 million years.
More on this Kewl geological Stuff! (http://www.ledger-enquirer.com/mld/ledgerenquirer/news/nation/8882362.htm)
<font size=4>Zircons worth more than diamonds for scientists</font>
By ROBERT S. BOYD
Knight Ridder Newspapers
WASHINGTON - Zircons: To lovers on a budget, they're low-cost jewelry. But to scientists, they're more precious than diamonds.
That's because they're the most ancient materials on Earth, guarding within their crystal depths an unequaled record of the infancy of our planet.
"The oldest dates we know about on Earth come from zircons," said John Hanchar, a geologist at George Washington University in Washington.
A fragment of zircon only a few thousands of an inch across that was picked up in the Jack Hills region of western Australia holds the record age of 4.404 billion years.
"Earth itself had formed less than 150 million years earlier," said Edmond Mathez, a geologist and zircon expert at the American Museum of Natural History in New York.
An even more archaic zircon, of extraterrestrial origin, was found in the remains of a 6-ton meteorite known as Vaca Muerta (Dead Cow) in the Atacama Desert of Chile. The gem was forged at least 4.6 billion years ago in the swirling disk of dust and rocks surrounding the sun that gave birth to the planets.
"It's the oldest thing ever dated in the solar system," Hanchar said.
Mathez called zircon "a unique clock (and) one of the most important tools geologists have for studying the long distant past."
Zircons have been used, for example, to date the assembly and movement of continents across the face of the Earth, according to a report by Richard Hanson, a geologist at Texas Christian University in Fort Worth, in the May 21 issue of Science.
A zircon crystal consists of the elements zirconium, silicon and oxygen. In nature it's yellow, gold or brown, but when heated turns a dazzling blue. The name comes from the Persian "zargun," meaning "gold color."
Zircons, incidentally, aren't the same chemically as "cubic zirconia," though both are used as cheap substitutes for diamonds in jewelry. Cubic zircon is a compound of zirconium, oxygen and, usually, yttrium, discovered in 1937. It lacks the silicon that's in a true zircon, and is, of course, very much younger.
According to the Complete Jewish Bible, zircon was one of 12 gemstones that Moses ordered put on a breastplate for his brother, Aaron, as described in the book of Exodus, 28:19 and 39:12. (Other biblical translations call the stone "ligure" instead of zircon. It's also known as jargon, hyacinth or jacinth.)
Geologists prize zircon for its durability. It remains unscathed while other rocks and minerals melt and are re-formed under the tremendous heat and pressure of continental shifts, mountain-building and the violent asteroid impacts of the hellish "Hadean" epoch during Earth's first 700 million years.
More on this Kewl geological Stuff! (http://www.ledger-enquirer.com/mld/ledgerenquirer/news/nation/8882362.htm)