Extraterrestrial Geology Meteorites in Indiana by Nelson R. Shaffer

Meteorites are rocks that fall to Earth from outer space. They have fascinated mankind since the beginning of time. They are scientifically valuable objects that help geologists understand the origins of planets and the processes that shape the Earth. Meteorites are rare and they exhibit special features that differentiate them from Earth rocks.

The Lafayette meteorite exhibits flow structures. Click to see a larger view.

Among characteristics that identify meteorites are a high specific gravity (especially true for irons); a dark color; and a dark glassy or dull crust if fresh or a rind of iron oxide (rust) if weathered. Most meteorites attract a magnet, although some only slightly. Many show aerodynamic shape, and their crusts may be marked with flow structures (see photo at left of Lafayette meteorite) or shallow depressions called "thumbprints" (see the South Bend meteorite).

The Hangman's Crossing meteorite exhibits features that are indicators of meteorites. Click to see a larger view.

Chondrules are almost certain proof that an object is a meteorite. A mixture of nickel and iron that appears as bright metallic flecks in a stone, or that makes up most of the object, also is a positive indicator. The Widmanstatten pattern (see the LaPorte meteorite) is also further proof.

Many tests needed to verify the identity of a meteorite should be performed by an experienced scientist, as much of the scientific information can be lost if the meteorite is improperly handled.

Where meteorites have been recovered in Indiana. Click to see a larger view.

Iron meteorites are mainly made of the nickel-iron minerals kacacite and taenite. But they may also contain other minerals and metals, such as cobalt, copper, and zinc.

Stony irons consist of about 50 percent nickel and iron and 50 percent silicate minerals. They are of two types: the pallasites and the mesosiderites. Pallasites have large (5-10 mm) glassy grains of olivine in a continuous matrix of nickel-iron. Mesosiderites contain small, bright, irregularly distributed metal flecks in a matrix of plagioclase and pyroxene minerals. Despite their apparent similarity, pallasites and mesosiderites appear to have different histories.

Stone meteorites are mineralogically the most complex and are the most abundant. They are dominantly made of silicates. Two main types—chondrites and achondrites—are recognized.

Chondrites, the most common (84 percent of falls), contain small (less than 1/8 inch) structured spheres called chondrules. Chondrules are found only in meteorites and contain some of the oldest material known to Man. Their origin is still uncertain, despite many theories proposed to explain them.

Achondrites—the second type of stone meteorites—contain silicates but do not contain chondrules. They resemble basalt from the Earth and represent about 8 percent of falls.

Many rocks and manmade objects appear similar to meteorites. Some suspected meteorites that proved not to be meteorites when examined closely at the Indiana Geological Survey were igneous rocks left by glaciers, sedimentary rock concretions, metallic alloys, and pieces of silicon. Even materials fused together by trash fires can resemble meteorites.

The Indiana Geological Survey will test suspected meteorites at no charge. Contact Dr. Nelson R. Shaffer at the IGS if you suspect you have a meteorite specimen.

WHAT TO LOOK FOR IN A METEORITE

Thin, dark glassy-to-dull coating or fusion crusts Flow structures or "thumbprints" on outside Aerodynamic shape High specific gravity

Metallic nickel-iron Widmanstatten pattern Small spherical chondrules Attracts magnets

Indiana Meteorites

Click linked names to see larger views.

Name	County	Fall or Find*	Date	Type	Comment
Hamlet	Starke	Fall	Oct. 13, 1959	Chondrite	Struck a house
Hangman's Crossing	Jackson	Find	1987	Chondrite
Harrison County	Harrison	Fall	March 28, 1859	Chondrite	Shower with only 4 stones recovered
Helt Township	Vermillion	Fall	1883-1884	Iron
Kokomo	Howard	Find	1862	Iron
Lafayette	Tippecanoe	Find	1931?	Achondrite	Found in collection at Purdue Univ.
LaPorte	LaPorte	Find	1900	Iron	Large piece buried and lost
Noblesville	Hamilton	Fall	Aug. 31, 1991	Chondrite	Nearly struck a boy
Plymouth	Marshall	Find	1893	Iron	Large piece buried and lost
Rochester	Fulton	Fall	Dec. 21, 1876	Chondrite	Only piece from large fireball
Rush County	Rush	Find	1948	Chondrite
Rushville	Franklin	Find	1866	Chondrite	Previously known as Brookville; renamed in 1903
South Bend	St. Joseph	Find	1915	Stoney Iron (Pallasite)

*Meteorites that are seen as they fall and are recovered shortly after landing are classed as Falls; those that are accidently found long after falling are classed as Finds.

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