Ramsdorf meteorite, Velen, Borken, Münster, North Rhine-Westphalia, Germanyi

Regional Level Types
Ramsdorf meteorite	Meteorite Fall Location
Velen	Town
Borken	District
Münster	Administrative District
North Rhine-Westphalia	State
Germany	Country

Ordinary Chondrite, brecciated and shocked (L6,br; S4)
Fall, July 26, 1958; 4682 g.

Falling from a clear sky with a few attendant whirring sounds a meteorite created a small depression accompanied by rising steam. The next morning at a depth of 40 cm a meteorite was removed from the ground. During the excavation the stone was broken into five pieces. While early studies seemed to establish that Ramsdorf was a somewhat brecciated, but otherwise ordinary 'Ordinary L6 (low iron) Chondrite' — subsequent studies have established that it is a very unordinary 'ordinary chondrite.' The primary mineralogical constituents are as expected — (1) Olivine and pyroxene dominate a few (relic) chondrules found in some areas while (2) olivine, pyroxene, Fe-Ni metal and intermixed feldspathic glass are prominent in the matrix. However, a closer look at the olivine and pyroxene 'crystals' and 'chondrules' reveal that much of the olivine and perhaps all of the pyroxene are recrystallized aggregates which are best explained as the partially or completely recrystallized product of a catastrophic shock-induced virtually complete melting followed immediately by rapid cooling of a small body (dia. ~2 m). This putative cooling occurred so quickly that many constituents remained more or less in place. Thus, for example, the outlines of large crystals of olivine ('ghosts') remain largely in place — but dark inclusions along the rim and along cleavage plains attest to the presence of mobilized, more volatile components. On the other hand, original plagioclase and Fe-Ni metal were apparently completely or almost completely melted. In the analyzed portions of the meteorite, the melted plagioclase now appears as a ubiquitous feldspathic glass. Likewise, Fe-Ni metal, particularly in matrix, is found almost entirely as small globules without the normal kamacite-taenite differentiation observed in most chondrites.

Many of the features outlined here can be explained by two shock events — (1) a heterogeneous level S6 shock event which melted almost all of the Ramsdorf material and (2) a later level S3-4 shock event which disrupted the reconstituted meteoroid. These explanations are also seemingly consistent with K-Ar dating studies indicating a catastrophic disruption of the L chondrite parent body ~400 Ma ago.

There are, however, some remaining interesting issues with respect to the minor phases which are scantily described in the literature — even in the superb Yamaguchi et al. (1999) article dedicated entirely to Ramsdorf. While metal, troilite, and chromite are specifically mentioned in places, small uncharacterized 'opaques' are ubiquitous in both the text and photographs and are generally not discussed. An exception are the tiny mineralogically uncharacterized phosphides discussed by Smith & Goldstein. [Normally ubiquitous phosphates, for example, are not mentioned in the text and the cited microprobe analyses do not include them.] For this reason, the observations of Ramdohr (1973) merit special attention. Using the oil-immersion techniques of reflected light microscopy, he was frequently able to make definitive determinations of opaque mineralogy [utilizing crystal form, delicate tints, petrological context …] impossible to make with the microprobe alone. In addition, working in his native Germany for several decades, Ramdohr was often able to combine observations from various specimens into his more comprehensive reports. It would be helpful if modern scientists would follow up with additional targeted studies of minor opaques (oxides, sulfides, Fe-Ni metal…) in this unusual stone.

As of early 2015 witnessed falls of 9 German L5 and L6 chondrites had been confirmed. As of 2000, only 486 grams (~ half of held masses) remained at the Naturhistorisches Museum in Wien (Vienna). Several additional small samples (99 g, 80 g & smaller) are found at 5 separate German museums.

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References