Noblesville meteorite, Hamilton Co., Indiana, USAi

Regional Level Types
Noblesville meteorite	Meteorite Fall Location
Hamilton Co.	County
Indiana	State
USA	Country

Ordinary chondrite, regolith breccia (H4-6,br; S1-S2)
Fell, 31 August 1991; 484 g, one stone

Two young boys were standing outside when a whirring stone passed over them and landed with a thud ~1.3 m away and created a small 9 cm wide, 4 cm deep hole. The meteorite, covered with a nearly intact fusion-crust, was an oddly oriented wedge-shaped stone (9 cm long x 7 cm wide, base ≤ 5 cm wide) with piezoglyphs on one side of the 'wedge'. Once identified, the meteorite attracted immediate scientific attention as it consists of a number of light-colored clasts within a darker matrix. The host matrix is classified as a type H4 meteoritic assemblage with incompletely equilibrated olivine (Fa16-21) and Ca-poor pyroxene (Fs7-23±3) while the clasts are dominated by more equilibrated olivine (Fa20) and orthopyroxene (Fs18-20). Both matrix and clasts are grossly similar in overall chemistry as the dominant olivine and pyroxene (~60-70 vol%) are accompanied by subequal amounts of plagioclase, Fe-Ni metal, and troilite. Fe-Ni metal is apparently mostly kamacite (Ni 4-7 wt%), but pertinent mineralogically definitive observations are missing from the cited sources. Accessory chromite is also reported. Most intriguing, the incompletely equilibrated host material appears to be only lightly shocked, while the more equilibrated light colored H6 clasts have been shocked to shock stage S2. This suggests that the H6 material was more highly shocked and reequilibrated during some previous era before impact(s) brought it to the surface of an H4-bearing meteoroid and, later, the joint assemblage eventually encountered the earth.

Noblesville is unusually rich in solar-wind noble gases suggesting a long surface exposure for the pre-impact meteoroid. Its reported cosmic ray exposure age of ~44 Ma is significantly older than that of most H chondrites, including other H chondrite regolith breccias. As of early 2016 only 2 witnessed meteorite falls had been listed exactly as 'H4-6' meteorites [i.e., an H4, H6 mixture] with the Meteoritical Bulletin Database. It seems evident that Noblesville has had a peculiar history during its long journey from its ancestral asteroidal home(s) to a small rock on an Indiana lawn.

13 meteorites, including 4 witnessed chondrite falls are listed as confirmed meteorites for Indiana. Hamlet, Harrison County, and Rochester are the other falls. However, the Lafayette (stone) meteorite, a Martian nakhlite identified after someone studied an odd stone in a geology drawer, is probably Indiana's most famous meteorite.

References

External Links

Other Regions, Features and Areas containing this locality