Peridot and Perseids
August 16, 2017
What Does the August Birthstone Have in Common With Meteors? Read On…
The peak viewing time for the annual Perseid meteor shower was August 12 this year, and that got me thinking about extraterrestrial influences on gems.
The August birthstone, peridot, is the gem variety of a mineral called olivine. It often occurs in volcanic rock formations called basalts, which are rich in the elements iron and magnesium - the iron being what gives peridot its beautiful green color.
Here on Earth, peridot is found in a wide range of areas, including Burma, Pakistan, Australia, Brazil, Kenya, Norway, and parts of the United States (this is only a partial list). But in rare cases, peridot has an extraterrestrial source - meteorites known as pallasites can contain pockets of olivine within their iron matrix, and sometimes the olivine contains gem-quality peridot.
Peridot Gemstones
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Meteorite With Olivine
The photo here shows a slice from the Esquel meteorite that landed near the Patagonian town of the same name in Argentina. It was found in 1951 by a farmer digging a hole for his water tank, and weighed about 1,500 pounds. It is considered one of the most beautiful meteorites ever found and is, of course, highly valued among collectors.
"Impact Glass" Used in Jewelry
Meteorites are also responsible for the formation of another unusual item used in jewelry: moldavite. Moldavite is part of a grouping called “impact glass”. When meteorites hit the earth, the surrounding rock is melted, and this can create what are called tektites. The impact of the meteor flings the molten rock into the upper atmosphere, where it cools, and then tektites rain down - sometimes spread over a distance of nearly 4,000 miles.
Moldavite, a green-colored variety of tektite, is formed this way. Most pieces of true moldavite are less than 100 grams. The fake identified below was for sale in Hanoi, (the size is the first clue that it is not real, but it was being sold as genuine).
According to a “Gems & Gemology” article by Jaroslav Hyrsl, the most famous gem-quality moldavites are from the southern Bohemia region of the Czech Republic. The meteor strike that created them occurred more than 14 million years ago and created the Ries crater in southern Germany.
Libyan Desert Glass
Another meteorite-formed treasure is Libyan Desert Glass. It is believed to have been formed 26 million years ago in an area near the border of modern-day Libya and Egypt. Although the precise origin of the glass is unknown, scientists have theorized that it is the result of a meteorite exploding in air - the heat of which melted the sand in the desert below. The pendant shown here is from the tomb of King Tutankhamen, and the centerpiece scarab is carved from Libyan Desert Glass.
Back to the Perseids...
The Earth’s orbit crosses the path of the Comet Swift-Tuttle, which is the largest known object to repeatedly pass by the Earth. It last passed by in 1992, and the next time will be in 2126. But it leaves behind a cloud of cosmic dust and debris, and every year the Earth passes through this cloud, resulting in the annual Perseid meteor shower.