[meteorite-list] Broek in Waterland meteorite fall is official
From: Galactic Stone & Ironworks <meteoritemike_at_meteoritecentral.com>
Date: Mon, 31 Jul 2017 17:30:48 -0400
The Broek in Waterland meteorite fall (Jan-11-2017) has been approved
and published in the Met. Bull.
Link - https://www.lpi.usra.edu/meteor/metbull.php?code=65715
Broek in Waterland 52?26?N, 4?59?E
Confirmed fall: 11 Jan 2017
Classification: Ordinary chondrite (L6)
History: A fireball was widely seen in Belgium and The Netherlands on
11 January 2017, at 17:09 CET, in a bright blue twilight sky. One
dashcam movie was obtained in Belgium. The next day, the owners of a
house near Broek in Waterland, just north of Amsterdam, noted damage
to the roof of a garden shed. They recovered a 0.5 kg stone. After
they reported their find to Niek de Kort of the Royal Dutch Astronomy
& Meteorology Association (KNVWS), it was identified as a meteorite on
3 February during an on-site visit by the classifiers. The stone was
given on temporary loan to Naturalis and 20 g was cut off with
permission of the owners for research purposes.
Physical characteristics: The stone is a solid, fist-sized mass 99%
covered by a thin, fresh fusion crust. The stone has faceted sides
(pointing to in-flight fragmentation) covered by fusion crust as well
as more rounded parts. The major flat surface shows regmaglypts. The
interior is light grayish in color. The surface is slightly scratched
by the impact and in 4 small spots the fusion crust has come off.
Petrography: (L.M. Kriegsman and M. Langbroek, NBC) The meteorite has
a dense, equilibrated texture in which chondrules can be distinguished
under the microscope. Chondrule types include porphyritic
olivine-pyroxene and barred olivine. In addition, single olivine
grains up to 1 mm are present. The interstitial space between olivine
grains is mostly occupied by plagioclase, with minor clinopyroxene
(augite) and low-Ca pyroxene. The outlines of chondrules are blurred
and merged with the matrix, which prevents their recognition in hand
specimen. Metal (kamacite, taenite) and sulfide (troilite) co-exist.
The smallest grains are dispersed homogeneously through the rock.
Larger grains (up to 2 mm) are also common. Other phases are chromite,
merrillite, and one large grain of chlorapatite. The large olivine
grains show undulatory extinction and are transected and locally
offset by small fractures reflecting shock effects. Most pyroxenes and
plagioclase also show undulatory extinction. In view of these
observations, we infer a shock state S3.
Geochemistry: Mineral compositions and geochemistry: Bulk Composition
(all in wt%) from 58 micro-XRF spot analyses, integrated with
microprobe and image analysis. SiO2 = 39.2 ? 0.3, MgO = 29.2 ? 0.5,
Al2O3 = 3.0 ? 0.1, CaO = 1.07 ? 0.02, Na2O = 1.4 ? 0.3, Cr2O3 = 0.40 ?
0.01, S = 1.9 ? 0.3, Ni = 0.43 ? 0.05, FeO = 17.4 ? 1, Fe = 6.1 ? 1.
Mineral data (EMPA) are Fa24.9?0.4 (n=3) for olivine, Fs21?1Wo2.0? 0.3
(low-Ca pyroxene, n=3); Fs8.6?0.2Wo44.2 ? 0.8 (augite, n=2) for
Classification: ordinary chondrite (L6)
Specimens: Main mass (504 g) with anonymous finder. Several small
fragments and powder totaling 20 g at NBC. The type specimen is a
fragment of 14.42 g.
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