Berthoud, Rare 2004 Eucrite Fell in a Colorado Horse Pen, Micromount

On the afternoon of October 5, 2004, Megan and Andy Clifford had just walked outside their home in Berthoud Colorado. They heard a loud whistling noise, followed by a dull thump. They went to investigate the sound and discovered a hole in the ground inside their horse pen. The fall was so fresh, the dust had not settled when they discovered the rock embedded a few inches into the ground. The stone was covered in a glossy black fusion crust. A sample of the stone was analyzed at the University of Arizona's Lunar and Planetary Laboratory and was revealed to be a Vestan eucrite achondrite.

Samples of witnessed fall eucrites from the USA are scarce, and very little of this stone ever made it onto the collector market. A few small samples and thin sections are in private hands.

Refer to the photo. The black centimeter cube is shown for scale and is not included. You are purchasing a single small fragment like the one shown. The fragment is enclosed in a capsule to protect it (the capsule can be opened). Your purchase will include a labeled gemjar for safe storage.


From the Meteoritical Bulletin entry on Berthoud :

Berthoud 40°1821.0’’N, 105°123.7’’W

Weld County, Colorado, USA.

Fall: 5 October 2004, ~13:30 local daylight time (UT-6)

Achondrite (eucrite)

History: A meteorite fell ~4 km east of Berthoud, Colorado. According to information from those who visited the site, Megan and Andy Clifford “had just walked out of their house when they were distracted by whistling noise and a thump. Megan observed some dust kicked up in a horse pen about 100 feet away. After a short search, they recovered the object.” (http://www.cloudbait.com/science/bermet.html). The meteorite embedded itself a few inches below the surface.

Physical characteristics: A single stone, 120 mm across, ~960 g was recovered soon after the fall. Fresh, glossy, black fusion crust covered the stone except for a small broken corner. The interior is medium gray in color.

Petrography: (D. H. Hill, UAz) Overall, texture is ophitic to subophitic with evidence of brecciation and recrystallization. The meteorite is shocked with occurrences of dislocated grains; fine melt veins run through the sample. Exsolution is observed in pyroxenes; several exhibit finely spaced fractures. Plagioclase contains many blebby inclusions. Accessory minerals include chromite, phosphates, iron sulfides, ilmenite, and silica.

Mineral compositions and geochemistry: (M. Killgore, UAz) Opx (Fs54.03En42.82Wo3.15); Cpx (Fs31.21En35.80Wo33.00); Plag (An82.72Ab16.04Or1.24); pyroxene molar Fe/Mn = 31. Oxygen isotopes (R. Greenwood, I. Franchi, OU) δ17O = 1.58‰; δ18O = 3.46‰; Δ17O = -0.227‰.

Classification: Achondrite (eucrite)

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