Achondrite: Stone meteorites lacking chondrules, which
have been heated and recrystallized.
asteroid: A body in space of an undefined larger size than a meteoroid
that is the source of most meteorites. Many but not all are found in the
asteroid belt between Mars and Jupiter.
ataxite: A subclass of iron meteorites which lack a Widmanstätten
pattern when etched because of too high a nickel content; which has allowed only
the mineral taenite to form during cooling.
Breccia: A rock composed of angular fragments from one or more source
rocks cemented together by fine material. Related terms would be Monomict
Breccia a rock formed from fragments of a single source rock. Polymict Breccia a
breccia formed from more than one source rock.
Chondrite: A major category of meteorites, characterized by the presence
of chondrules.
Chondrules: Small spherical structures consisting of mineral grains that
are found in Chondrite meteorites.
fusion crust: The melted outer surface of a meteorite formed by the heat
and ablation of passage through the atmosphere.
hexahedrite: A subclass of iron meteorite that consists of only kamacite,
because of too little nickel in the original bulk alloy before cooling. It lacks
a Widmanstätten pattern when etched.
mesosiderites: A subclass of stony-iron meteorites, where silicate
mineral inclusions are surrounded by a continuous nickel-iron matrix.
meteor: The light phenomenon seen in the sky caused by the passage of a
high velocity particle through the atmosphere.
meteoroid: A body traveling in space smaller than an asteroid.
meteorite: A natural object that has spent a long period of time in
space, which survives the fiery passage through the atmosphere to be found on
the Earth's surface.
NWA: This abbreviation stands for North West Africa. It
is followed by a number which May be an approved name by the Nomenclature
Committee of the Meteoritical Society or May only be a provisional number and
not officially a recognized meteorite.
octahedrite: A subclass of iron meteorite in which the original nickel
content was proper for the formation of both taenite and kamacite nickel-iron
minerals to crystallize during cooling. Octahedrites show a Widmanstätten
figure when etched.
pallasite: A subclass of stony-iron meteorite characterized by the
presence of olivine crystals surrounded by nickel-iron metal.
polymorph: A mineral with the same chemical makeup, but because of
exposure to extremely high pressure or other condition has been altered to
exhibit a different crystal structure, and often higher density.
regmaglypts: Often called thumbprints. They are flight marks from the
ablative passage of the meteorite through the atmosphere. Characteristically
they are circular or oval depressions on the surface of the meteorite. They are
proportional in size to the size of the meteorite they are found on.
strewn field: An area on the surface of the Earth where individuals and
fragments of the same meteorite are found. It is a limited area usually of
elliptical shape where larger masses are found at one end and smallest masses
are often found at the opposite end, with grading and mixing of sizes
in-between.
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