Meteorite Glossary

The Meteorite Glossary is here to give a helping hand on some of the meteorite and tektite terms you may find on our pages and specimen descriptions. We know there may be some meteorite and tektite definitions not listed in our Meteorite Glossary so if you find a term that is not listed please let us know through our 'Contact Us' page.

A

Ablation:

The process during the passage of a meteoroid through the atmosphere where melting and vaporization removes material from its surface.

Acapulcoite:

One of the primitive achondrite type meteorites, characterized by partial chnodrite textures and partial melting but chondrite composition.

Achondrite:

Meteorites formed from an igneous source rock and lacking condrules, group includes lunar and planetary meteorites.

Aerolite:

This is an older word used for stony meteorites. It is not often seen in use today but can be seen often in articles and books up to around 1950.

Amphoterite:

This is the obsolete term used for the LL class of ordinary chondrites.

Angrite:

An achondrite meteorite type characterized by calcium-titanium-aluminum rich pyroxene abundance.

Armored Chondrule:

A chondrule with is covered on its surface by a layer of nickel iron. It will show when cut as a chondrule encircled by a thin ring of shiny metal.

Asteroid:

A body in our solar system composted of either metal or rock which is smaller than a planet yet larger than a meteoroid. Though the size ranges are not clearly defined and usage of the two terms overlap.

Astrobleme:

The scar on the surface of the Earth or other body in space caused by the impact of a meteoroid or asteroid. Synonymous with Impact Crater.

Astronomical Unit:

This is the distance from the Sun to the Earth; approximately 93 million miles.

Ataxite:

An iron meteorite class that is high in nickel content, and exhibits no Widmanstatten Pattern when etched.

Australite:

Tektites found in Australia are referred to by this term. They are by current evidence related to and from the same origin event as those from Indochina and the Philippines. Among the various forms that australite occur in are the very prized flanged buttons. These are round or oval and have been ablated on one side. They have a ring of melted glass around the edge.

B

Basalt:

A common volcanic rock, lava is general basaltic. Some of the planetary and lunar meteorites are basalts.

Bolide:

A very bright meteor that may be associated with detonations and a smoky train. Often producing meteorites. Fireball

Brachinite:

One of the primitive achondrite type meteorites. It is composed of almost only olivine.

Breccia:

In contrast to conglomerates which are rocks made of varying sizes of round cobbles. Breccias are rocks made of angular chunks of rocks. Breccias made of one type of rock pieces are called monomict breccias. Rocks made of chunks from more than one type of parent rock are called polymict breccias.

C

CAI:

Calcium-Aluminum Inclusions are very evident light colored inclusion commonly found in carbonaceous chondrites. They are often irregular in shape.

Caliche:

Meteorites are often found in desert areas covered or partially covered in a white encrustation of calcium material. This material is Caliche. It is not unlike common lime build up in pipes and on plumbing fixtures, but forms naturally because of repeated wetting and drying where calcium is present in the soil.

Carbonaceous:

A family of chondritic meteorites that contain several percent carbon by weight and are among the most primitive of meteorites.

Chondrules:

Small round and oval structures of crystal grains found in most chondrite type meteorites.

Coesite:

A high pressure form of silicon dioxide usually diagnostic of an impact event on rocks containing it. Forms at shock pressures of 30-50 gigapascals.

Cohenite:

An iron nickel carbide mineral found in some iron meteorites.

Cosmic Rays:

Radioactive particles that travel through space. They are the cause for the formation of isotopes of certain elements present in meteorites.

Crater:

The bowl shaped scar formed when an asteroid strikes the Earth or other body. Usually refers to a different feature than the simple impact pit formed ay a small meteorite. Craters generally refer to a feature formed by explosive force.

Cumulate:

Rocks composed of crystals that have grown and accumulated in a cooling magma.

D

Differentiation:

Term used to describe the layered nature of a body or planet in space which has zones of differing density. For example the Earth shows differentiation in that it has a crust a mantel and a core.

Diogenite:

An achondrite type meteorite characterized by abundant magnesium-rich pyroxene

E

Electrophonic Noise:

This term is used to describe phenomenon reported to have accompanied the passage of meteoroids through the atmosphere. The witnesses will state that they have hear sounds and felt physically things at the same time as they saw the meteor in the sky. The difference in the speed of sound and that of light would preclude this if the sensations were sonic. Therefore the cause of these sensory responses travels at light speed. The best current guess is that they are electrically caused by the meteoroid's passage through the upper atmosphere.

Enstatite:

A magnesium silicate mineral. One of the orthopyroxenes which are found in meteorites. E chondrites are stone meteorites with a high percentage of enstatite.

Eucrite:

A class of achondrite meteorites that is similar in composition to basalt lavas found on Earth.

F

Fall:

The recovered meteorites of an event that was seen by eye witnesses.

Find:

The recovery of a meteorite that was not witnessed but found later.

Fireball:

A very bright meteor.

Fragmentation:

The breakup during passage through the atmosphere of the cosmic body that forms the many pieces that may later be found as individual meteorites of the event.

Fusion Crust:

The melted rock or metal exterior surface of a meteorite which forms from the heating of high velocity entry into the Earth's atmosphere.

G

Graphite:

A mineral form of carbon characterized by a flat sheet like crystalline structure. It occurs in iron meteorits as blebs and nodules and abundantly in carbonaceous chondrites.

H

Hexahedrite:

A type of iron meteorite containing a low nickel content. It exhibits on Widmanstatten Pattern when etched.

Howardite:

A meteorite classification of achondrite composed of a mixture of eucrite and diogenite angular clasts making it a breccia.

I

Igneous Rocks:

Rocks that form by heat and melting. The two types of igneous rocks are volcanic and plutonic. Volcanic rocks as the name implies are eruptive rock, like lavas. Plutonic igneous rocks form below the surface by the slow cooling of rocks at great depth. Volcanic rocks are fine grained because of quick cooling. Not time for crystals to grow more than microscopic in size. Plutonic igneous rocks have larger crystals through very slow cooling and long growth times.

Impactite:

A glassy rock that is found in association with impact structures and craters, it is formed from the melting of native rocks during the impact of asteroids. It can be very well melted found as glassy and solid or may be poorly melted and bubbly. sometimes it will contain spheroids of nickel iron from the impacting body.

Iridium:

A rare metallic element. It is found in meteorites, especially iron meteorites.

J

No Terms

K-T boundary:

The point in the geological record ending the Cretaceous period and the beginning of the Tertiary period. Sometimes this layer in the rock is marked by a relatively thin layer of iridium rich clay which may be from deposits of dust and soot resulting from an asteroid impact.

L

Lawrencite:

A material that forms in meteorites as a product of weathering and decomposition. Similar to rust on iron, lawrencite forms as chemicals which are present eat away at the metals of the meteorite.

Lechatelierite:

A fused silica glass that is formed by the high temperatures of an asteroid impact striking rocks that are high in quartz; like sandstones and granites.

Lithology:

The physical description of the composition of a rock.

Lodranite:

One of the rare primative achondrites, related to acopulcoites. Lodranites are often more coarse grained than acopulcoites. They are depleted in plagioclase feldspar.

M

Magnetite:

An iron mineral that is found in meteorites of certain types and is found in the fusion crust of meteorites. It occurs naturally as large grains and nodules on Earth and being magnetic and responsive to a magnet as well as black and heavy makes it a first rate impostor of a true meteorite.

Matrix:

The material of a meteorite that fills the spaces between chondrules and inclusions. It is made of much smaller mineral particles than the chondrules and inclusions themselves.

Mesosiderite:

A class of stony-iron meteorite that contains silicate and other mineral inclusions as a major portion of its mass.

Meteor:

The luminous phenomena in the sky caused by the high velocity passage of a cosmic body through the atmosphere.

Meteorite:

The rock or iron body that survives the passage through the atmosphere and reaches the ground.

Meteoroid:

A body in space that is smaller than an asteroid.

Moldavite:

The name for tektites found in the Czech Republic. They are generally green in color. They may have formed from material melted in the Ries Impact event in Germany.

N

Nakhlite:

The sub-family of planetary (martian) meteorites that are the N of SNC achondrites. Often a greenish color they are made of mostly augite a clinopyroxene. Name is derived from Nakhla a meteorite which fell in Egypt.

Neumann Lines:

A fine line structure that is often the only thing seen when a hexahedrite is etched. It is found on the kamacite crystals only.

O

Octahedrite:

A broad class of iron meteorites which is characterized by the presence of both Taenite and Kamacite nickel iron minerals in the crystal structure of the meteorite. Octahedrite meteorites will normally show a Widmanstatten pattern when sliced polished and etched. Size of the crystals determines the sub-class from coarsest to fine octahedrite.

Olivine:

A magnesium-iron silicate mineral commonly found in meteorites. It occurs as microscopic crystal grains in chondrites and as large often well formed crystals in pallasites.

Oriented:

A meteorite which makes it passage through the atmosphere in a stable orientation toward the ground may receive characteristic ablation features from being melted mostly on one surface. Among these features are a cone shaped or a rounded front surface, radial lines of melting in the front surface, and a rolled over lip of melted material which has cooled around the circumference of the back side. Sometimes these features maybe exaggerated to actual splattering or bubbling of material onto the back side as well as deep radial furrows in the front surface. Oriented meteorites should be recognized as distinct from meteorite fragments which may show ablation on a surface that is similar in appearance but does not indicate that the meteorite as a whole is oriented.

P

Pallasite:

A class of meteorites characterized by a mixture of large olivine crystals in a matrix of nickel iron.

Petrology:

The study of the nature of minerals in rocks, or the minerals which are found in meteorites

Plessite:

A fine grained mixture of taenite and kamacite that often forms triangular fields bordering the taenite and kamacite crystals of octahedrite meteorites. But it is not a mineral itself instead it is made of the other two nickel iron minerals.

Polymorph:

A mineral with the same chemical composition of another but often with a different density and hardness. Often polymorphs in meteorites are formed by high pressure and high temperature. Diamond and graphite are common polymorphs of carbon.

Pyroxene:

A magnesium-iron silicate mineral family but distinct from olivine found in many different forms in meteorites.

Q

No Terms

R

Regmaglyphs:

Flight marks produced by ablation during the passage of a meteoroid through the atmosphere. Often looking like thumbprints pushed into the surface, but, they may also be long straight grooves or radiating lines or pits of odd shapes.

Rumurutite:

A rare class of chondrite meteorites that are very low in metal, almost all iron is found in the minerals and not as metallic.

S

Schreibersite:

A shiny-brittle iron-phosphide mineral found in iron meteorites. Slivery-white in color. It often occurs as long needles and is commonly seen ringing nodules of graphite.

Shattercone:

A peculiar texture imparted to rocks which have suffered impact shock. Shattercones resemble cones inside of cones like stacked paper cups. Often they will be found as mass of cones next to each other in a layer at crater sites.

Shergottite:

A rare sub-class of planetary (martian) achondrite. It is a basaltic igneous rock with plagioclase and pyroxene. The S in SNC type meteorites.

Shock Veins:

Veins of melted material that run through a meteorite. they are caused by shock induced melting and often follow preexisting fractures that were in the mass before the impact which caused the shock. They can be few in number or many which can resemble a spider's web. They are often glassy, often black but can be metallic.

Siderite:

The obsolete term used for iron meteorites. Commonly used prior to about 1950.

Siderolite:

The obsolete term used for mesosiderites or stony-iron meteorites.

Stishovite:

A high pressure mineral form of SiO2, formed by the pressure of an impact event. Now considered along with coesite to be nearly diagnostic for impact origin of suspect geologic formations.

Strewnfield:

The area on the ground surface that meteorites and fragments from a single fall are contained within. It has the same meaning as distribution ellipse, which puts emphasis on the fact that a strewnfield is often oval in shape. The largest specimens to be found are often at the end of longest flight. Thus direction for the entry of the meteoroid into the atmosphere can be roughly determined from the pattern in the strewnfield of recovered pieces.

T

Tektite:

A natural glass object formed by the melting of native rocks during some asteroid impacts. Some tektites receive aerodynamic shapes as the still plastic but cooling glass falls back to the surface from very high altitude. Other tektite glass may be from a melt sheet formed near the impact site.

Troilite:

A common mineral found in all types of meteorites. Troilite is chemically FeS and is related to Pyrrhotite which is found on Earth. It is bronze in color and only 4.6 in hardness. Dissolvable in a nitric acid solution it will stain the surface of iron meteorites during etching making it easy to positively identify. Often found in association with graphite and schreibersite in iron meteorites.

U

Ureilite:

A class of achondrite meteorites characterized by a carbon rich matrix and the presence of microscopic diamonds.

V

No Terms

W

Widmanstatten Pattern:

A pattern displaying the crystal structure of the various nickel-iron minerals in octahedrite iron meteorites. It can be seen when a smooth polished surface is chemically etched. On occasion it can be seen in the way a meteorite fragment has weathered.

Winonanite:

A class of achondrites that are very rare and primitive in their structure. They are partially melted and have a relationship to IAB irons.

X

No Terms

Y

No Terms

Z

Zenolith:

An inclusion in a rock or meteorite that is not related to the rest of the rock or meteorite material. often in meteorites it is seen as an oval or irregular shaped mass that has a strikingly different texture and color from the rest of the meteorite.