Studies on an Iron Meteorite found near Blacksburg, VA. Mark A. Stegner and Protip K. Ghosh. Geology Department. Results: 1. Strong magnetic response 2. Atmospheric ablation marks and regmaglypts (Fig. 1) 3. Glassy rind (Fig. 1)
Studies on an Iron Meteorite found near Blacksburg, VA
Mark A. Stegner and Protip K. Ghosh
1. Strong magnetic response
2. Atmospheric ablation marks and regmaglypts (Fig. 1)
3. Glassy rind (Fig. 1)
4. Metallic core (95%) composed of iron and nickel (Fig. 2)
5. Minerals identified:
Kamacite Fe (93-96%) Ni (4-7%) iron rich (Fig. 3 A,B)
Taenite Fe (60-80%) Ni (20-40%) nickel rich (Fig. 5 A,B,C)
Schreibersite Fe (55%) Ni (14%) P (31%) accessory (Fig. 6 A,B)
Unidentified Silicate Mg, Si, P, S silicate (Fig. 7)
Troilite Fe S
Other small minerals embedded in Taenite and Schreibersite.
6. Structures seen:
Widmanstätten pattern (Very coarse) (Fig. 2)
Neumann Lines (Fig. 4)
7. Chemical analysis:
Ni (mg/g) Co (mg/g) Ga (g/g) Ge (g/g) Cu (g/g) Cr (g/g)
67.3 6.3 168 293 123 5.3
1. The sample is a meteorite collected near Blacksburg, Va.
2. The magnetic strength separates this sample from slag material that
may have similar appearance.
3. The presence of regmaglypts (thumb-shaped indentations caused by
melting on atmospheric entry) along with the smaller ablation pits,
demonstrate that this sample is extra-terrestrial.
4. The glass rind on the outside surface also points to fusion during
atmospheric entry. This rind also prevented weathering.
5. The freshness of the iron and nickel, seen on the inside, also points to
a non-terrestrial origin. It is very rare to find such un-oxidized
6. The Widmanstätten pattern, which is a pattern produced between the
kamacite and taenite interface, confirms this is a meteorite.
Widmanstätten patterns develop in a zero-G environment and on very
7. The presence of Neumann Lines, which appear as fine parallel lines
running in (up to) six directions, indicates impact with another body.
These lines are caused by twinning due to post-consolidation
8. The high Fe-Ni constituents identify this as an Iron meteorite.
9. The band-width of the kamacite within the Widmanstätten pattern
(average > 2 mm), and the content of Ni around 6.7%, indicates that
this is a coarse octahedrite.
10. The Ga-Ni and Ge-Ni concentrations, when compared to other
reported octahedrite values, points to the fact that this is a IAB type
iron. (Fig. 8) The Ga content is rather high, but high Ga values
are known in some octahedrites.
11. Schreibersite, and minor amounts of silicate minerals, are known to
occur in octahedrites.
In early 2004 the Marshall University Geology Department obtained a sample of a meteorite found by Mr. Skip Spencer of Charleston, WV. It was found near Blacksburg, VA. The purpose of this study was to confirm that the sample was a meteorite and to classify it as to its type. The sample was highly magnetic, had a black ‘fusion crust’, and showed the presence at the surface of ‘regmaglypts” (thumbprint shaped atmospheric burn marks).
The meteorite was cut in two with a rock-saw and then polished to a high sheen with 1 alumina paste. The polished surfaces were etched using a solution of ethyl alcohol (90%) and nitric acid (10%). The etched samples were then studied with a polarizing microscope and with a Scanning Electron Microscope (SEM-EDS).
Based on preliminary chemical, mineralogical, and structural studies, this meteorite can be classified as a coarse to medium Octahedrite, type IAB. Minerals identified are the two Fe-Ni minerals kamacite (Ni,< 6%) and taenite (Ni, > 25%), schreibersite ((Fe, Ni)3 P), and a silicate mineral (probably olivine ((Mg, Fe)2 Si O4 ). Etching clearly showed the Widmanstätten pattern, formed by the intergrowth of kamacite and taenite lamellae. Also seen at places are Neumann Lines, fine sets of parallel lines created within kamacite due to the development of twinning.
Further analyses of trace elements (Ge, Ga, Ir) is being conducted to determine the exact classification and also to determine whether this sample is related to an octahedrite (Dungannon) previously reported from Virginia.
Fig. 2 Sample after cutting, polishing, and acid etching.
Fig. 1Outside surface: before preparation.
Fig. 3B Kamacite S.E.M. X-ray spectrum analysis (Iron - Nickel)
This study was conducted to determine if this sample is a meteorite. Finding that it is a meteorite an attempt will be made to identify the minerals present and classify the meteorite into its chemical and structural classes.
Fig. 3A Kamacite: under S.E.M. Magnified x 100
Fig. 4 Neumann Lines: under S.E.M. X 500
Appear as closely spaced parallel groves.
Fig. 5A Taenite Composition: under S.E.M. X-ray analysis
Note that lighter areas mark higher concentration.
1. This sample is certainly a meteorite.
2. The Widmanstätten band-width, and the Ni, Ga, and Ge contents, all
classify this as an IAB octahedrite.
3. The chemical composition of this meteorite is markedly different from
the only other iron meteorite (Dungannon) found in Virginia
Ni (mg/g) Co (mg/g) Ga (g/g) Ge (g/g) Cu (g/g) Cr (g/g)
This sample: 67.3 6.3 168 293 123 5.3
Dungannon: 69.5 4.72 78.8 332 153 27
4. Although the analytical method (ICP) used for this study is somewhat
semi-quantitative, there is a strong chemical indication that this
meteorite found near Blacksburg is distinctly different from the
5. A strong case can be made that this is a previously unreported meteorite
6. Further work will involve chemical analysis by a better quantitative
technique, and a closer control on the exact location and date of
Fig. 5B Taenite Analysis: Note the significantly higher nickel.
Fig. 5C Taenite: S.E.M. X 350 Note the scale bar’s size.
The light colored areas are Schreibersite inclusions.
Fig. 7 Silicate: under S.E.M. X 100 Note texture.
Final Classification: Iron Coarse Octahedrite Type 1AB
New England Meteoritical Services; www.meteorlab.com
Weir, David. Meteorite Information; www.geocities.com/CapeCanaveral/9278/menu2.htm
Darling, David. Classification of Iron Meteorites; www.daviddarling.info/encyclopedia/I/iron_meteorite.html
McDonough, W.F. Comp. Model for the Earth’s Core. Treatise on Geochemistry, Vol. 2, p.547-568, 2003
‘Skip; Spencer (Retired Geologist) Who kindly supplied the original specimen.
Dr. Aley El-Shazly (MU Geology) For help with analyses.
Dr. Mike Norton (MU Chemistry) Standars for analysis.
Fig. 6A Schreibersite band: S.E.M. X 200
Fig. 6B Schreibersite analysis: Note the presence of phosphorous.