) ( Singular nouns: Fr- météorite;
Ger- Meteorit/Meteorstein; Nor- meteoritt;
Rus- )
METEORITES
(See the addendum at the end of this
entry. The information included seems better presented as a unit,
as it is there, than to integrate it with the text of the main part of
this
entry.)
A. Meteorite - Octahedrite egg (height - 5.8 cm) exhibiting Widmanstätten pattern; fashioned from Gibeon meteorite from Namibia (formerly German Southwest Africa). Claude Pelisson collection. (© photo by Claude Pelisson)
B. Iron meteorite (width - ca. 20 cm), an octahedrite, which has been etched to exhibit the Widmanstätten pattern, from Staunton, Augusta County, Virginia. The dark area is troilite (meteoric pyrrhotite -i.e.,stoichiometric FeS). Smithsonian Institution collection (#NMNH808). (photo from Brian Mason, courtesy of Smithsonian Institution)
DESCRIPTION: The designation meteorite is applied to rocks of extraterrestrial origin. Of all the diverse kinds of meteorites, octahedral iron-nickel meteorites are the most prized as gemrocks; this is so because some of their surfaces, when appropriately etched, exhibit highly desired patterns -- e.g. those usually called Widmanstätten lines (see, especially Figure B). However, other kinds of meteorites -- e.g., chondrule-bearing chondrites -- have also been fashioned, albeit less often, into both gemstones and ornamental pieces. Criteria generally suggested for recognizing meteorites in the field include the following: 1.they may lie within impact craters, even small ones; 2.they may have dull, commonly black, fusion crusts; 3. their surfaces may exhibit a pattern of lines (etc.) that appear to represent flowage, apparently imposed by aerodynamic forces while they were solidifying; [and] 4. they may contain metallic iron, which is magnetic and commonly rusted. None of these criteria, however, is absolute, so if a loose rock has one or more of these features, the best advice is to pick it up and take it to a professional who can submit it to diagnostic tests.
OTHER NAMES: Most meteorites have been given binomial designations: The first name is the geographic locality where the meteorite fell (or was found); the second name is the meteorite category to which the given stone belongs -- e.g., the Staunton octahedrite (an iron-nickel meteorite that fell in Staunton, Virginia). Descriptions of compositions and textures of diverse meteorites is beyond the scope of this document; several are described and illustrated in the REFERENCES cited at the end of this entry.
Two meteorites that are especially well known for having had their fragments fashioned into cabochons etc. for pendants, rings, and for larger items such as paperweights, as well as being sold with their natural shapes as souvenirs are:
USES: Jewelry, paper weights, etc. -- e.g., a
free-form made from a pallasite (stony iron meteorite) from in Esquel,
Argentina (see Koivula, Kammerling and Fritsch, 1993).
Buchner
et al. (2012) note that "stony meteorites were used to
carve birds and other works of art, jewelry [,] and knifes were
produced of meteoritic iron[,] for instance[,] by the Inuit
society." They also include a pair of photographs of the piece,
which is called the "iron man" (Fig. 3), which is reproduced here,
courtesy of Elmar Buchner (p.c., email dated
9/22/2013 1:36 PM) -- see
below. Data about the composition of
the meteorite from which this small statue was carved, and information
about the
probable source of this meteorite are given in their paper (op. cit.).
Photographs
and descriptive information
about a carving characterized as " 'Iron Man' Buddhist Statue" have
also been posted on the internet (e.g., Pappas,
2012), who repeats some additional informatio much of which is from
Buchner et al. (op. cit.). In any case, the statue/caving
is "about
9.5 inches (24 cm) tall and weighs about 23 pounds (10.6 kg)", the
material is an "ataxite" meteorite that appears to
have been one of many fragments known to have been found along the
Siberian-Mongolian
border, and these meteorites are hypothesized to have
fallen "10,000 to 20,000 years
ago." Pappas also includes information about, for example how
(and, by implication why) the piece got to Nazi Germany.
C. "Ataxite" meteorite carving. See information in above paragraph. These photos, originally published as Figure 3 in the cited article by Buchner et. al. are reproduced here courtesy of Elmar Buchner.
OCCURRENCES: To clarify a somewhat fuzzy nomenclature: Meteors are solid masses of extraterrestrial origin that are visible as they enter or move through the Earth's atmosphere. Meteorites are those masses that have impacted the Earth's surface. (In addition, the term meteorite is applied widely to such masses that have impacted other celestial bodies such as the moon and other planets.)
NOTEWORTHY LOCALITIES: Meteorites are found where they have fallen.
REMARKS: The Widmanstätten patterns exhibited on surfaces of octahedrite iron-nickel meteorites are produced by etching with some caustic solution.
As recently as the 18th century A.D., meteorites were thought to have several origins quite different from that now accepted. Three examples are 1.they are gifts or missiles from the gods and thus to be worshiped or feared; 2.they come from distant volcanoes -- e.g., one that fell in 1795 near Wold Cottage, Yorkshire, England was interpreted to have come from Mount Hecla in Iceland; [and] 3.they are merely terrestrial rocks swirled up and dropped by powerful hurricanes.
Along this line, although this may not be the best venue to air a conclusion: Although the "great stones [the Lord threw down] from heaven" that are noted in the Old Testament (Joshua, 10:11) have been cited as probably representing a meteor shower, some dissenters have questioned them and suggested that the stones more likely represent a shower of large hailstones. On the basis of climatic data and the absence of recorded meteorites from the area in question (Yehoshua Kolodny, personal communication, 1997), I consider the hailstone possibility to be more likely correct.
Another interesting anecdote about meteorites involves the usually sagacious Thomas Jefferson: He is said to have remarked, when he heard that Yale professors Benjamin Silliman and James Kingsley had reported a meteorite fall at Weston, Connecticut, "It is easier to believe that Yankee professors would lie, than that stone would fall from heaven."
Whatever, more than two centuries ago, the Czech E.F. Chladni (1794) concluded that several iron masses found on Earth came from cosmic space. Unfortunately, his conclusion was published several decades before anyone was ready to accept such a possible origin. -- As noted by Brown (1974), "Chladni's unorthodox views came under fire and one [unnamed] critic remarked 'He contradicts the entire order of things and does not consider what evil he is causing for a moral world.'." Current consensus vindicates Chladni's conclusion, and today it is generally accepted that meteorites have impacted Earth intermittently throughout geologic time. Indeed, well documented evidence exists for impacts that occurred at least 1.85 billion years ago (see, for example, Hodge, 1994), and supporting evidence includes the presence of spatially associated meteor craters, impactites, and tektites (see TEKTITE entry); and the fact that some recent falls have been directly observed.
To date, more than 150 meteor craters, ranging up to 200 km (~125 mi.) in diameter and from 1.85 billion to less than 50 years old, have been identified on Earth. Three of the best known craters are 1.the Barringer crater, located a few miles southeast of Flagstaff, Arizona, which has been a tourist attraction for many years; 2.the Chicxulub crater, centered about 50 km north of Merida, on the Yucatan Peninsula, Mexico, which has been correlated with the widespread ejecta hypothesized to have been a primary cause of the extinction of dinosaurs; [and] 3.the1947 Sikhote Alin crater, about 150 miles south of Chabarovsk, in Far eastern Russia, which has been memorialized by a USSR postage stamp that shows an artist's depiction of the meteor during its flight through the atmosphere.
SIMULANTS:
***Alloys -- e.g., bronze (copper-tin) and brass (copper-zinc). The metal dog-shaped pendant represented to have been made from a meteorite in Tibet during the 15th Century is a good example; it is now know to be a copper, tin, zinc and lead alloy (Johnson and Koivula, 1996, p.288-289). Another example is the group of bomb-case fragments described by Norton (1994, p.171). - [Most alloy simulants can be ruled out as meteorites (at least as octahedrites) because they do not exhibit the typical Widmanstätten pattern; additionally, if the piece shows evidence of chemical deterioration, the color of the residue should be checked -- iron-nickel of meteorites typically develop a brownish rust whereas most common alloys do not.].
***Droplets from welding activity. - [do not really resemble meteorites either physically or chemically].
***Fused terrestrial iron. - [Widmanstätten patterns and nickel are absent.].
***Slag -- e.g., from blast furnaces - [None I have found recorded really resembles meteorites.].
REFERENCES: Brown,
1974;
McCall, 1973; Norton, 1994.
Addendum: A peridot-bearing pallasitic
meteorite from Argentina has been fashioned into some attractive
decorative articles including gemstones (see Fig. 1, p. 209
in the referenced article). This, the Esquel meteorite, was discovered
in 1951; there are, of course, several other similarly
constituted meteorites known from several places on Earh.
Peridot
is the name widely applied to the gem varieties of the mineral
olivine. Olivine is an iron-magnesium silicate that is relatively
common in rocks such as basalts and is a major constituent of the
Earth's mantle. Pallasitic meteorites are stony-iron meteorites
that consist of olivine within an iron-nickel matrix
Meteorites of this type have long
been a source of peridot used in jewelry. However, it is only
fairly recently that the complete rock -- i.e., the peridot within its
matrix -- has been fashioned into decorative items and gemstones that
have been marketed rather widely. .
REFERENCE: Shen, Koivula
and Shigley, 2011.
R. V. Dietrich © 2015
Last
update:
23 September 2013
web page created by Emmett Mason