Glossary
Because I sell meteorites, I sometimes get asked questions like “what does NWA stand for?” or “what is cutting dust?”. Some of the terminology we use can be confusing to someone new to the hobby. To further complicate the issue, many of the phrases we use are slang without textbook definitions (the phrase “Bessey speck” comes to mind).
So, I’ve decided to put together this glossary of meteorite terms. This list is a work in progress, and it is not meant to be authoritative or complete. If you have comments or suggestions, I would appreciate them – please see the contact page.
ablation – the removal of outer surface layers of a meteorite as it travels through the Earth’s atmosphere.
ANSMET – the Antarctic Search for Meteorites, a U.S. program which had found thousands of meteorites since the 1970’s.
Bessey speck – a meteorite sold as a tiny fragment; popularized by meteorite dealer Dean Bessey in the late 1990s. See speck.
CAI – abbreviation for calcium aluminum inclusion. These inclusions are characteristic of CV carbonaceous chondrites.
caliche – calcium carbonate deposits that may wind up on the surface of a meteorite during the process of weathering.
chondrule – the building block of chondrite meteorites; a spherical mass of rock formed by rapid cooling and solidification of partly molten droplets in space.
complete slice – a slice which has been cut from an individual meteorite. These are highly desirable, because such a slice is rimmed with the exterior of the meteorite (usually fusion crust).
crust – see fusion crust.
cutting dust – the remaining saw dust after a meteorite has been sliced on a lapidary saw. For rare meteorite types, such as Lunar and Martian meteorites, many meteorite dealers save this dust and sell it as a collectible. Often sold in small glass vials.
cutting loss – the portion of a meteorite that is lost as a result of slicing on a lapidary saw. Even with thin lapidary blades, each cut of the saw pulverizes a thin portion of meteorite. Also see cutting dust.
desert polish – a smooth, shiny surface found on some meteorites as the result of windblown sand and dust in desert regions. May also be referred to as “wind polish”. Not to be confused with desert varnish or fusion crust.
desert varnish – a thin, glossy, brownish coating on the outer surface of some desert meteorites and rocks. It is the result of trace amounts of minerals carried on the wind and deposited on the surface of the stone over a long period of time (see weathering). There is some overlap between the terms “desert varnish” and desert polish; both are typically seen as a glossy brown coating that is sometimes mistaken for fusion crust by novice collectors. (thanks to MikeG)
dust – see cutting dust.
end cut – a piece of a meteorite which has been cut off of an individual with a single cut. End cuts display the interior of the meteorite on the cut surface and the exterior of the meteorite on the opposite side.
etched meteorite – an iron or stony-iron meteorite which has been soaked in an acid bath to reveal the Widmanstatten pattern.
fall – Typically, the word “fall” is short for “witnessed fall”. This word is used to make the distinction from “finds“, which are meteorites that were not witnessed hitting the earth. Falls are highly collectible, because they often have interesting stories or historical significance. Also, many falls are fresh, because they may be picked up shortly after impact.
find – The word “find” is used to describe meteorites which were not witnessed impacting the earth. Instead, finds are discovered at a later date. Most known meteorites are finds.
flow lines – a surface feature seen on the fusion crust of some oriented meteorites. As a meteorite falls through the Earth’s atmosphere and forms fusion crust, the exterior of the meteorite becomes molten. If the fall is oriented in a particular direction (i.e. not tumbling), fine lines may form where drops of molten crust flow away from the leading face. When the crust quickly cools and solidifies, we are left with these lines indicating the direction of flow.
fossil meteorite – term used to describe a meteorite with a very old terrestrial age and high amount of weathering. Fossil meteorites have been heavily altered during their time spent on Earth, and they may be found underground or as part of a rock conglomerate. Well-known examples include Al Haggounia 001 and NWA 2965.
fragment – a piece of a meteorite which has not been sliced, but which is not an individual. Some meteorites are found as fragments, because individuals may break up during impact. Other meteorites may be found as individuals, but then later be broken into fragments for resale.
fresh - adjective to describe a meteorite which has not undergone a significant amount of weathering. Fresh meteorites are highly desirable among collectors.
full slice – see complete slice.
gem case – a type of small plastic case which is popular among meteorite collectors. These are typically round, 1-2″ in diameter, and lined with white or black foam. A clear removable lid is used to protect and display the specimen.
hammer - see hammer fall & hammer stone.
hammer fall – a meteorite fall in which at least one of the meteorites (see hammer stone) hit a manufactured object or animal. Popular examples include Peekskill (hit a car), Claxton (hit a mailbox), Sylacauga (hit a woman), and Valera (hit a cow).
hammer stone – the meteorite(s) from a hammer fall which impacted a manufactured object or animal. These stones are highly collectible due to the rarity of these occurrences.
HED/HEDO – a group of achondrites which are thought to be from the asteroid 4 Vesta; named for the types Howardite, Eucrite, Diogenite, and Olivine Diogenite.
IMCA – the International Meteorite Collectors Association, a group of collectors and dealers promoting authenticity.
impact glass – see tektite.
individual – an entire meteorite which has not been broken or sliced, or which has been broken or sliced only minimally (i.e. a chip or small window).
indochinite – a popular variety of tektite found in southeast Asia. Indochinites are dark, pitted, and come in a variety of shapes. They are the most affordable type of tektite.
Libyan desert glass – a type of impact glass found in the western desert of Egypt near the Libyan border (part of the Great Sand Sea). The origin of Libyan Desert Glass has been debated over the years. The generally accepted theory is that energy released from a meteorite explosion melted the surrounding desert into sheets of glass. As the years passed and sands moved, this glass broke into smaller pieces and was sandblasted into smooth shapes.
matrix – in stone meteorites, the fine-grained material found between chondrules and inclusions.
membrane box – a type of clear display box popular among meteorite collectors. A clear membrane keeps the specimen suspended in the middle of the box, thereby making it visible from all angles. Sold at membranebox.com.
meteorwrong – nickname for any object which resembles a meteorite, but is not of meteoritic origin. This may include earth rocks, slag, and industrial waste.
micro - a small – usually thumbnail sized or smaller – piece of a meteorite. Meteorites this size are popular among collectors due to their affordability; there are dozens of ordinary chondrites sold in this size for under ten dollars each. Micros are often sold in gem cases.
moldavite – a popular type of tektite found in the Czech Republic. They have a distinctive translucent green appearance and are sometimes used in jewelry.
NWA – abbreviation for Northwest Africa, a location where many meteorites have been found. “NWA” is typically followed by a number, indicating its official name (e.g. NWA 869). There are also many meteorites from Northwest Africa which are unclassified; in this case, they may be referred to as “NWA unclassified” or “NWA xxxx”.
oriented – adjective used to describe a meteorite which fell through the Earth’s atmosphere in a somewhat steady direction (i.e. not tumbling). As a meteorite falls through the Earth’s atmosphere and forms fusion crust, the exterior of the meteorite becomes molten. When the crust quickly cools and solidifies, we are left with telltale signs of how the meteorite fell. Indicators of orientation include flow lines, a roll-over lip, and/or an overall “head shield” shape.
paired meteorites – two meteorites which are classified separately but are from the same meteorite fall. For example, this may occur when pieces of the same meteorite are found by different meteorite hunters and both send pieces in for classification.
paleo-meteorite – see fossil meteorite.
parent body – the asteroid or other celestial body where a meteorite is derived from. For example, the asteroid Vesta is the parent body of all howardite meteorites, and Mars is the parent body of all SNC meteorites.
part slice – a portion of a complete slice of a meteorite. In other words, a slice which is not entirely rimmed with the exterior (usually fusion crust) of a meteorite.
petrologic type - a numerical scale for measuring how much meteoritic material has altered from its original state while in space. The scale ranges from 1-7, with 3 being the most unaltered state. Petrologic types 1 and 2 indicate that the material has been altered by the presence of water, while types 4-7 indicate alteration due to heat.
provisional – a classification and/or name which has not been approved yet by the nomenclature committee of the Meteoritical Society.
regmaglypts – the smooth pitting or “thumb prints” which form on the exterior of many meteorite during passage through the Earth’s atmosphere. These tend to be shallow in stone meteorites, but deeper and better defined in iron meteorites. A classic example of an iron meteorite with well-defined regmaglypts is Sikhote-Alin.
riker mount – a type of display case popular among meteorite collectors. Riker mounts are flat, black leatherette cases with a removable glass lid. Because they are flat, riker mounts are typically used for complete slices and part slices.
shale – iron meteorite material which has undergone severe weathering until virtually all that remains is rust.
shattered crystal fragments – a type of small, shiny, jagged iron meteorite specimen. These are formed when an iron meteorite is frozen using liquid nitrogen then shattered with a hammer. This process is typically only used on Nantan and Campo del Cielo – two inexpensive iron meteorites which are known for being prone to surface rust.
shrapnel – a jagged, distorted fragment of iron meteorite which results of explosive break up during the fall. The most popular example of meteorite shrapnel is Sikhote-Alin. Some pieces recovered from the Sikhote-Alin fall are shrapnel, and others are individuals.
skeleton – nickname for a piece of a pallasite which has been weathered until the olivine crystals are essentially gone; all that remains is an irregularly shaped iron structure. A popular example of a meteorite which is often found in skeleton form is the Imilac pallasite.
slickensides – a smooth, striated surface which is the result of a rock fracturing. These are rarely seen in meteorites, but there are a few popular examples such as Zag and Tamdakht.
SNC – the group of all Martian meteorites; named for the three main types: Shergottite, Nakhlite, Chassignite.
speck – a meteorite sold as a tiny fragment; popular for rare meteorite types such as Martian meteorites and Lunar meteorites. These tiny pieces are often sold by the milligram (1mg = 0.001g) or sold without being weighed at all.
strewn field – when a meteorite falls in more than one piece, the roughly elliptical area in which meteorites are found.
tektite – a natural glass rock found on Earth which is the result of a meteorite impact. There are several different types of tektites – the results of different impact events. Some of the most popular include Indochinites, Moldavites, and Libyan desert glass.
terrestrial age – the length of time that a meteorite has spent on the Earth before being discovered.
toolbox meteorite – a collector term for a meteorite which was used as a tool before it was identified as a meteorite. A famous example is the Tucson iron, which was used as an anvil.
thin section – a small, very thin meteorite part slice prepared for viewing under a microscope.
thumb prints – see regmaglypts.
TKW – the Total Known Weight of all of the pieces of a particular meteorite. This is a useful measure for how large a meteorite fall was, and it often (but not always) is a measure of how readily available the meteorite is for collectors.
unclassified – a meteorite which does not have an official or provisional classification. The most common example of unclassified meteorites are NWA unclassified stone meteorites. Due to the large influx of meteorites from that region, meteorite dealers have not taken the time to put every stone through the lengthy classification and approval process.
weathering – the effects of long term exposure to the Earth’s environment on a meteorite. This may include rusting, sand blasting, caliche deposits, or other effects depending on the type of environment surrounding the meteorite fall.
Widmanstatten pattern – a characteristic cross-hatched pattern visible on etched slices of most iron meteorites. This pattern is the result of soaking in an acid bath, which affects taenite and kamacite components of the meteorite differently.
window - a flat surface where a meteorite individual or fragment has been cut or ground, revealing the interior.
References:
- Field Guide to Meteors and Meteorites by O. Richard Norton
- The Internet Encyclopedia of Science