Beautiful Esquel

Pallasites are gorgeous meteorites but none more than Esquel.

While her name means “thorn” because of the local bushes in the area, Esquel has come to be known for beauty, stability, and lasting quality.

Figure 1.

Like a stained-glass church window, olivine crystals set in a nickel-iron matrix.

Named after the bushes and local town, no one remembers the meteorite fall, but in 1951 a farmer uncovered Esquel while digging a hole for a water tank or livestock pond.

Not the most glorious beginning for a dramatic pallasite, mud and rough edges. But, Esquel was purchased and brought to the United States in 1992 by meteorite hunter Robert Haag, who cut and polished her into brilliancy.

All pallasites like Esquel come from the boundary between the silica rich mantle and the iron-nickel core of a planet-like body. They provide a snapshot of a dynamic process – where iron mixed with olivine – and at the moment when the mixture solidified.

Eventually, pallasites were blasted away from their parent body by a devastating impact with another planetoid or asteroid.

Here's where pallasites are found in their parent bodies:

Figure 2.

Here's another photo of this meteorite in our educational collection:

Figure 3. 28.5 grams.

So, as you can see, Esquel is a type of stony-iron that when cut and polished shows its beautiful yellowish green olivine (peridot) crystals. Are there other types of stony-irons?

Side Trip - Esquel, Argentina

Esquel is also a town in the northwest of the province of Chubut, in the Argentine Patagonia, a geographic region containing the southernmost portion of South America. Located in Argentina and Chile, the Patagonia comprises the Andes mountains to the west and south, and plateau and low plains to the east....

The town's name derives from a Mapuche term meaning "thorn," which refers to the characteristics of the local plants, including several spiny bushes.

Figure 4.

The founding of the town dates back to the arrival of Welsh immigrants in Chubut in 1865.

Just The Specs

Pallasite - essentially olivine and pyroxene and metals

Olivine (66%)
Iron (23.5%)
Nickel (8.5%)
Schreibersite (0.76%)
Troilite (0.46%)
Chromite (0.31%)

Total iron accounts for 19.22% of its volume.

The silicates are concentrated in the boundary regions between the grains of olivine and the metallic matrix.

What's interesting about Esquel is that there are very few small olivine crystals in the pallasite. Scientists believe that the parent body must have endured several impacts during its history. Consequently, the small fragments broken by the impacts fused together during subsequent increases in temperature.

Found 1951
Esquel, Argentina

Terms

As with other meteorites, the unique composition of Esquel can teach us about minerals, structure, our solar system, and ultimately the world we live on.

Definition of Chromite

n. A black submetallic mineral consisting of oxide of chromium and iron – also called chromic iron.

Photo from http://www.neab.net/oldgeo/locality/finland/horsmana.htm

Definition of Olivine

n. A yellowish green mineral consisting of magnesium iron silicate; a source of magnesium.

Here's an example:

Photo from NASA Ames Research Center, Tom Trower.

Definition of Schreibersite

n. A mineral occurring in steel-gray flexible folia (thin layers). It contains iron, nickel, and phosphorus, and is found only in meteoritic iron.

This cut surface shows numerous troilite (see below) and also schreibersite inclusions. Often the different structures are separated by elongated schreibersite worms.

Photo from http://www.meteorite-recon.com/en/meteorite_santa%20fe.htm

Definition of Troilite

n. Native iron protosulphide, FeS. It is known only in meteorites, and is usually in embedded nodular masses of a bronze color.

Here's a picture of a troilite inclusion:

Photo from http://www.lexic.us

Links

Here's a link to the American Museum of Natural History, discussing pallasite formation and giving three theories to why no meteorites have been found from an asteroid's olivine mantle?

WHY THE STRANGE MIXTURE?

http://www.amnh.org/exhibitions/permanent/meteorites/planets/mantle.php

Here's the International Meteorite Collectors Association (IMCA):

http://imca.repetti.net/metinfo/index.html

Here's a good reference dictionary:

http://www.lexic.us/

Here's a link to the New England Meteoritical Services. Contact Russell Kempton, Director, and explain what you are interested in:

http://www.meteorlab.com

Figures & Acknowledgments

Figures

Figure 1. Photo by New England Meteoritical Services. www.meteorlab.com
Figure 2. Illustration @ Colin Smith.

Figure 3. Photo by New England Meteoritical Services. www.meteorlab.com
Figure 4. Photo from http://outdoors.webshots.com/photo/1236517067063150413JMZVSc