Nine Signs of a Real Extraterrestrial Alien
To know how to identify a meteorite, you first need to know the types of meteorites. There are three main types of meteorites: stony meteorites, iron meteorites, and stony iron meteorites. As the name suggests, stony-iron meteorites are typically composed of a 50/50 mixture of iron and silicate minerals. This is a very rare type of meteorite, accounting for about 1-5% of all meteorites. Identifying such meteorites can be very difficult. They resemble a metal sponge with a silicate substance in its pores. There are no rocks on Earth similar in structure to stony-iron meteorites. Iron meteorites make up about 5% of all known meteorites. This is a monolithic piece of an alloy of iron and nickel. Stone meteorites(ordinary chondrites) make up the majority, 80% to 95% of all meteorites that fall to earth. They are called chondrites because of the small spherical mineral inclusions called chondrules. These minerals are formed in a vacuum environment in zero-gravity space, so they always have the shape of a sphere. Signs of a meteorite It is clear that an iron meteorite is the easiest to identify, and a stone meteorite is the most difficult. Only a highly qualified specialist can recognize a stone meteorite for sure. However, even an ordinary person can understand that this is an alien from outer space by the simplest signs of a meteorite:
1. Meteorites are heavier than earthly rocks. This is caused by the greater density that meteorites have compared to terrestrial rocks.
2. 2. The presence of smoothed depressions, similar to finger indentations on plasticine or clay - the so-called regmaglypts. These are indentations, ridges, buckets, and depressions on the surface of a meteorite that are formed through a process called ablation. This happens at the moment when a meteoroid passes through our atmosphere. At very high temperatures, the less dense layers on the surface of the stone begin to melt, and this creates round, depressed depressions.
3. Sometimes the meteorite has an oriented shape and resembles a projectile head.
4. If a meteorite fell not too long ago, then there will probably be a melting crust on its surface - dark thin shell about 1 mm thick. Typically, this dark black fusion crust looks very similar to coal on the outside, but if the meteorite is a stony type, it usually has a light colored interior that looks just like concrete.
5. The fracture of the meteorite is often gray, sometimes small balls about 1 mm in size are visible on it - chondrules.
6. In almost all heavenly wanderers, inclusions of metallic iron can be seen on the polished section.
7. Meteorites are magnetized, and the compass needle next to them is deflected.
8. Over time, the meteorite changes its color, which becomes brown and rusty. This is caused by an oxidation reaction.
9. In meteorites that belong to the iron class, on a polished and acid-etched section, you can often see large metal crystals - Widmanstätten figures.
People have always worshiped what fell from the sky. There are a lot of references to heavenly stones among Christians, Jews and Muslims. The Egyptians, Indonesians, Indians and many other peoples made weapons from meteorite iron. And also - meteorites were called Christ's stone. They were infused with water and even crushed to add to food.
Black stone- a Muslim shrine, a stone of forgiveness, according to legend, sent to Adam and Eve by God, mounted in the eastern corner of the Kaaba at a height of 1.5 m and enclosed in a silver frame. The visible surface of the stone has an area of approximately 16.5 x 20 cm.
According to legend, the Black Stone was once white, but gradually it turned black, saturated with human sins. According to one version, the “black stone” is a huge meteorite.
Today we are talking about meteorite jewelry that is extremely fashionable today. The demand for them is unusually high on both sides of the ocean. Meteorites are of interest not only to scientists, but also to jewelers, watchmakers, and accessory manufacturers. What is the secret to the success of this star stone? And what is a meteorite?
A meteorite, a celestial body, fragments of comets and even planets that fell to Earth without burning up in the atmosphere. Meteorites can range in size from less than 1 millimeter to several meters, but usually upon entering the Earth's atmosphere, large meteorite bodies crumble into small fragments weighing no more than a few kilograms.
Meteorites can be stone (chondrites), consisting mainly of olivine and pyroxenes, they are the most common - more than 90% fallen meteorites- these are stone. They may contain a mineral such as chrysolite, and even, extremely rarely, diamonds.
Chondrites they are called because of the specific structure - they consist of numerous rounded formations - chondrules, about 1 mm in diameter (rarely larger). It is believed that chondrites formed directly from the protoplanetary cloud that surrounded and surrounded the Sun, through the condensation of matter and the accretion of dust with intermediate heating.
Achondrites- it's simple stony meteorites, they are few in number, only about 7%. These are fragments of protoplanetary (and planetary?) bodies that have undergone melting and differentiation by composition (into metals and silicates). There are also iron-stone meteorites, so-called pallasites.
The most rare (5-6%) iron and iron-nickel meteorites, consisting of almost pure iron with a small (up to 5%) admixture of nickel. The rarest - iron meteorites, consisting of almost pure iron (no more than 1.5%).
We know that a creative tandem – Man and Nature – is working to create works of jewelry. But sometimes a third participant, the Cosmos, is also included in this process, and the result of this triad is extraordinary jewelry of truly unearthly beauty!
A meteorite is perceived as material evidence of the existence of the Universe. Planets, comets, galaxies seem to an ordinary person something abstract and infinitely distant. But when we pick up a meteorite, we feel the reality of the Universe and feel involved in it. The fall of meteorites accompanied many significant events in history, which indicates the influence of Heaven on the life of our Planet.
In ancient times, people saw meteorites as the material embodiment of heavenly gods, and this made meteorites an object of worship - religious buildings were erected at the site of their fall, and from iron meteorites Divine cult talismans and amulets were made. Comparing meteorite iron with gold, silver and copper, our ancestors could not help but admire its superiority in hardness, strength, and fire resistance.
Ancient legends convey legends about the “heavenly” origin of the weapons and armor of the great conquerors - the leader of the Huns Attila, Tamerlane, King Arthur... Archaeologists know of products consisting of almost 90% iron, created long before the Bronze Age. A dagger found in the tomb of the Egyptian pharaoh Tutankhamun, who lived in the 14th century BC. was probably made from an iron-nickel meteorite.
And in most of the gold jewelry found during excavations of the pyramids in Egypt, sacred Scarab beetles were inserted, made from “Libyan glass” - tektite, a glass-like mineral formed during the explosion of a meteorite on the surface of the earth.
In all the mythologies of antiquity, the fall of a meteorite was interpreted as hierogamy- the sacred marriage of the God of Heaven and the Goddess of the Earth. And going deeper into the earth, the meteorite seemed to symbolize the union of heaven and earth, the birth of a new life.
In magic, a meteorite is considered as a very strong and active metal, but disordered and little susceptible to outside influence, and therefore has protective properties. And if you wear a meteorite in the form of rings, pendants and other amulets, then demons, ghosts and other creatures who are afraid of the powerful, projective vibrations of this metal will not come near you!
King Solomon had a favorite ring, Alexander the Great had a crown, and both kings never parted with their talismans and endowed them with magical power. Both the ring and the crown, according to legend, were made... from a star, i.e. from meteorite iron.
Even in ancient times, meteorites were ground into powder and drunk as a cure for many ailments, and people still believe in such magical properties meteorites. When a meteor shower fell over Uganda on August 14, 1992, local residents made a powder from the stones that supposedly helped against AIDS, malaria and other diseases.
Currently, designers and jewelers are increasingly using meteorites, both iron and stone. For example, the famous American designer Paris Kain, founder of the jewelry brand Abraxas Rex. His works have been recognized by famous fashion brands for many years. Starting out by creating futuristic accessories for Calvin Klein and Alexander Wang, Abraxas Rex now produces exceptionally original jewelry from the most unusual materials, including meteorites and dinosaur bones. And stone meteorites, when cut, can resemble a black diamond.
Paris Kane decorated his first ring with a stone discovered near a Buddhist monastery in Kyoto, Japan - and has since turned the use of unusual materials into a special tradition. Their Jewelry Kane is made from an alloy of platinum and silver, 18-karat green gold, fragments of meteorites and ... dinosaur bones.
Prices for Abraxas Rex jewelry range from $1,250 for a platinum and silver pendant to $16,000 for a unique ring set with a meteorite fragment. Abraxas Rex jewelry is sold in the largest stores in Europe and the USA - Barneys in New York, Browns in London, Colette and Rick Owens in Paris.
A unique feature of Swiss RIEMAN watches is the stylized Dzeta symbol in silver or gold on the dial at 7 o'clock and on the crown. In many ancient and modern cultures a sign of a similar shape has magical meaning cosmic force, energy, protection and justice, his image serves the function protective amulet. In astrology, this sign is associated with Jupiter and the symbol of lightning, in ancient runes - with the “heavenly arrow of strength,” victory and power. This is a symbol of connection with the Sun, with the stars, with the entire Cosmos. But in RIEMAN watches this sign is really connected with Space: Dzeta on the dial of RIEMAN watches contains the “DNA of the Universe” - a little iron from the mysterious Campo del Cielo meteorite, which fell to Earth many thousands of years ago.
The value and popularity of meteorites are growing year by year, which means that tomorrow jewelry with a meteorite will cost even more. But why do many people want to have a meteorite, wear rings and jewelry made from meteorites? The answer lies in the extraordinary qualities of this stone, and here are just a few of them:
- a space stone is considered a magnet that attracts the attention of the opposite sex, and a pendant with a meteorite is considered protection against celibacy;
- using meteorite jewelry as an amulet allows you to protect yourself and your family members from misfortunes;
- parapsychologists call the meteorite an activator unusual opportunities person;
- The meteorite is credited with the properties of a panacea for all diseases - star stones are not only worn on oneself, but also consumed internally, crushing the meteorite into powder;
To have and wear a meteorite means to join the secrets of the Earth and Space! And today, designer jewelry with a meteorite is not just a prestigious accessory and a truly unearthly gift! Jewelry with a meteorite is a touch to the Mystery of the Cosmos!
Kazdym A.A.
List of used literature
- Kazdym A. Heavenly stones - meteorites in jewelry // Navigator of jewelry trade, 2011, No. 1-2 (January-February). pp. 96-100
- Kazdym A.A. Tunguska meteorite // Kontinent Media Group, No. 44, November 23, 2012, http://www.kontinent.org/article_rus_50af5a8069629.html, 2012
- Senatorova O., Zarzhetskaya-Dokuchaeva O., Kazdym A. Jewelry stones. Directory. M.: 2009.
When finding a suspicious stone or piece of iron, many are immediately interested in how to identify a meteorite. To really make sure that this is an object that is of extraterrestrial origin, you need to figure out what they are like. Another parameter that those lucky enough to find a meteorite want to know about is its cost. But it is not so easy to determine it at home. How much a meteorite is worth can depend on many factors, some of which are not so obvious at first glance.
meteorite flight
Definition of meteorite
Meteorites are divided into three categories: stone, iron and mixed. Since iron is found in most meteorites, the first thing to do is to check whether the stone you find has magnetic properties. In addition, meteorites are typically heavier than rock and have a higher concentration of nickel than any terrestrial rock.
The largest meteorite found is Goba; according to some sources, its weight was about 60 tons.
The most difficult question to answer is how to recognize a meteorite at home if you come across a sample of a mixed structure. Typically the ratio of iron and silicate materials is 1 to 1. And they exist in two types: pallasite and mesosiderite. The latter are rare.
The most common are stone meteorites; they account for up to 95% of all finds. Iron meteorites are found in 5% of cases.
This is what part of a meteorite looks like
If you examine the meteorite under a magnifying glass, you will find spots of iron inside it, but in addition, there are also mineral inclusions that have a spherical shape and are called chondrules.
The material surrounding such patches of iron and chondrule is called the matrix. Chondrules are formed in a vacuum environment and at zero gravity, which is why they have this shape.
On the surface of the meteorite you can see what is called the melting crust of the meteorite. It is a thin veneer of black material and is formed during the entry of a meteoroid into the earth's atmosphere. Outwardly, it is very reminiscent of coal, and if the meteorite is of the stone type, it has an outer part that looks like concrete.
Another important indicator, which helps at home to attribute the find specifically to a meteorite - these are regmaglypts. These are structures formed as a meteorite passes through the atmosphere. They may appear as grooves, buckets, ridges or depressions on the surface. Such structures form where the surface was less dense and melted under the influence of high temperatures. Such indentations have another name - fingerprints. They were given this name because the finger usually fits well into such structures.
If the meteorite is cut, Widmanstät structures can be seen inside. This is a type of metallographic structure of alloys that has correct location elements in the form of plates, polygons or needles. They form an alloy of crystalline structures. Such patterns appear when, under the influence low temperatures space, different elements of crystalline structures do not have the opportunity to mix.
Other factors that will help you identify a meteorite at home are:
- The thickness of the melting crust should not exceed 1 mm. If it is thick, then it is an earth stone.
- Meteorites that fell not so long ago should not have cavities. However, if the sample has been stored in the ground for a long time, it may have them due to corrosion of metallic inclusions.
- So far, layered meteorites have not been found; any find with such a structure is of terrestrial origin.
- A sample with inclusions of blue or red color is not a meteorite.
- If a stone is similar in structure to metal and is not magnetic at all, then it is not a meteorite. Of course, there are non-magnetic metals, but they haven't fallen from the sky yet.
- Meteorites have a characteristic shape. It is difficult to describe it, but having some experience in this, it will be very difficult to confuse the meteorite with an earthly stone.
These are characteristics that indicate that you have a meteorite in your hands. If you still doubt the origin of your find, then you should turn to professionals. There are entire communities that are engaged in the search and study of meteorites. People interested in this are called meteorite hunters.
Any meteorites after the search must be examined and recorded. This is done to help scientists study them. After registering them with the scientific community, documents will be issued for the meteorite confirming the authenticity of the find. So you can ask for such documents when purchasing.
Meteorite Sikhote-Alin
Meteorite price
As with other collectibles, its price can be determined by various factors. Among them: the type, rarity of the find, the history associated with its fall, aesthetic appeal, weight and many others.
- The cost of most stone meteorites is low. Unclassified stony chondrites will have a price of about half a dollar per gram. On some meteorites that have a more attractive appearance, it can be 2 or 3 times larger.
- Iron meteorites are somewhat more expensive. For example, the Sikhote-Alin meteorite, which fell in 1947 in the territory Soviet Union and was found in whole fragments, costing approximately $2-3 per gram. It is highly prized among collectors as it has sculptural qualities.
- Pallasites - one of the subtypes of stony-iron meteorites - are much more expensive. Firstly, because they are rarer, and secondly, because of their content precious metals. They are much more beautiful, and when processed they have excellent qualities - strength and resistance to destruction. Specimens of this extraterrestrial breed are valued at $20-40 per gram.
- Particularly rare meteorites are those that are of lunar or Martian origin. They cost even more. The price of such meteorites exceeds the price of the most popular precious metal - gold - 40 times, and reaches $1000 per gram.
One of the criteria for evaluating a meteorite is the unusual nature of its origin. For example, a meteorite that, when it fell, destroyed someone’s apartment or car, can be highly valued. The assessment of the meteorite will also be influenced by whether it was noticed, or even better, captured on a photo or video camera during its fall. It is interesting that some collectors are looking for just such a meteorite, which fell on some significant date for them. A stone that is described in the scientific literature will be more expensive.
Sometimes the world's largest museums buy meteorites from hunters or sales dealers. Such purchases subsequently have a label or museum number, which can also significantly affect their value. Particularly prized are meteorites from the American Museum of Natural History of New York City or the Natural History Museum of London.
Some of the most famous meteorite collectors were Harvey Nininger and Glenn Goose. They had large collection. If such a well-known collection contained and referenced a particular meteorite specimen, then the remaining specimens of that meteorite immediately became much more valuable.
One day in 1992, a meteorite fell on the luggage compartment of a car in Kuntukki. The weight of this meteorite was a little more than twelve kilograms, but it itself belonged to unremarkable chondrites. The meteorite was named Peekskill. However, its provenance makes it unique and coveted by collectors around the world. If an ordinary stone meteorite can be purchased for only 0.5-1 dollar per gram, then a Peekskill sample can be purchased 100-200 times more expensive, and it will not be easy to find someone who will sell it to you.
One more important point What can significantly increase the value of a found meteorite is the unusualness of its shape. Basically, it is iron meteorites that have particularly beautiful shapes. Some collectors are so attracted to them that they are willing to pay considerable sums for them. A meteorite acquires this shape during fiery processing - passing through the densest layers of the atmosphere. As it flies, such a hot iron meteorite can acquire rather unusual sculptural and aesthetic forms.
If you want to buy a meteorite
When purchasing, it is important to remember that since meteorites are a very expensive product, the reputation of the seller comes first. The world is bought and sold every day a large number of fake meteorites, so be careful.
Meteorite lots at the largest auctions in the world are often replete with such announcements: “meteorite of excellent museum quality” and so on. But this is in best case scenario craftiness. Very often this turns out to be just a hoax. There are very few examples of meteorites of this quality in the world. Before making a purchase, carefully study the seller’s rating and reviews, and also do not hesitate to ask questions about the origin of the meteorite and its accompanying documents.
Websites that sell meteorites and give truthful information about them have the IMCA logo. This logo signifies that the seller is a member of the International Meteorite Collectors Organization and adheres to its code. Such an organization ensures that its conditions are met, primarily the reliability of information about the sample being sold. Such a logo will guarantee that you will not part with your money in vain.
Finding a real meteorite is not so easy. Every day, 5-6 tons of such objects fall to the ground, which is approximately 2 thousand tons per year. Most meteorites that fall to Earth weigh from a few grams to several kilograms. It is important to contact only trusted dealers, and you can find them using coordinates on collector communities. You can check the authenticity of a meteorite at home, but it is better to contact a specialist.
Iron meteorites are the most large group finds of meteorites outside the hot deserts of Africa and the ice of Antarctica, since non-specialists can easily identify them by their metallic composition and large weight. In addition, they weather more slowly than stony meteorites and, as a rule, have significantly big sizes by virtue of high density and strength, preventing their destruction when passing through the atmosphere and falling to the ground. Despite this fact, as well as the fact that iron meteorites with a total mass of more than 300 tons account for more than 80% of the total mass of all known meteorites, they are relatively rare. Iron meteorites are often found and identified, but they account for only 5.7% of all observed impacts. In terms of classification, iron meteorites are divided into groups according to two completely different principles. The first principle is a kind of relic of classical meteoritics and involves the division of iron meteorites by structure and dominant mineral composition, and the second is a modern attempt to divide meteorites into chemical classes and correlate them with certain parent bodies. Structural classification Iron meteorites are mainly composed of two iron-nickel minerals - kamasite with a nickel content of up to 7.5% and taenite with a nickel content of 27% to 65%. Iron meteorites have a specific structure, depending on the content and distribution of one or another mineral, on the basis of which classical meteorology divides them into three structural classes. OctahedritesHexahedritesAtaxitesOctahedrites
Octahedrites consist of two metal phases - kamacite (93.1% iron, 6.7% nickel, 0.2 cobalt) and taenite (75.3% iron, 24.4% nickel, 0.3 cobalt) which form a three-dimensional octahedral structures. If such a meteorite is polished and its surface treated with nitric acid, the so-called Widmanstätt structure appears on the surface, a delightful play geometric shapes. These groups of meteorites vary depending on the width of the kamasite bands: coarse-grained nickel-poor broadband octahedrites with band widths greater than 1.3 mm, medium-textured octahedrites with band widths from 0.5 to 1.3 mm, and fine-grained nickel-rich octahedrites with band widths less than 0.5 mm. Hexahedrites Hexahedrites consist almost entirely of nickel-poor kamasite and do not reveal a Widmanstätten structure when polished and etched. In many hexahedrites, after etching, thin parallel lines appear, the so-called Neumann lines, reflecting the structure of kamasite and, possibly, resulting from impact, a collision of the parent body of the hexahedrite with another meteorite. Ataxites After etching, ataxites show no structure, but, unlike hexahedrites, they are composed almost entirely of taenite and contain only microscopic kamasite lamellae. They are among the richest in nickel (the content of which exceeds 16%), but also the rarest meteorites. However, the world of meteorites is amazing world: paradoxically, the most big meteorite on Earth, the Goba meteorite from Namibia, weighing more than 60 tons, belongs to a rare class of ataxites.
Chemical classification In addition to the iron and nickel content, meteorites vary in the content of other minerals, as well as in the presence of traces of rare earth metals such as germanium, gallium, and iridium. Studies of the ratio of trace metals to nickel have shown the presence of certain chemical groups of iron meteorites, each of which is believed to correspond to a specific parent body. Here we will briefly touch on the thirteen identified chemical groups, it should be noted that about 15% of known iron meteorites do not fall into them meteorites that chemical composition unique. Compared to the iron-nickel core of the Earth, most iron meteorites represent the cores of differentiated asteroids or planetoids that must have been destroyed by catastrophic impact before falling to Earth as meteorites! Chemical groups:IABICIIABIICIIDIIEIIFIIIABIIICDIIIEIIIFIVAIVBUNGRIAB Group A significant part of iron meteorites belongs to this group, in which all structural classes are represented. Particularly common among meteorites of this group are large and medium-sized octahedrites, as well as iron meteorites rich in silicates, i.e. containing more or less large inclusions of various silicates, chemically closely related to uinonaites, a rare group of primitive achondrites. Therefore, both groups are considered to originate from the same parent body. Often IAB group meteorites contain inclusions of bronze-colored iron sulfide troilite and black graphite grains. Not only does the presence of these vestigial forms of carbon indicate a close relationship of the IAB group with the Carboniferous chondrites; This conclusion can also be made by the distribution of microelements. IC Group The much rarer iron meteorites of the IC group are very similar to the IAB group, with the difference that they contain less rare earth trace elements. Structurally, they belong to coarse-grained octahedrites, although IC group iron meteorites with a different structure are also known. Typical for this group is the frequent presence of dark inclusions of cementite cohenite in the absence of silicate inclusions. Group IIAB Meteorites of this group are hexahedrites, i.e. consist of very large individual kamasite crystals. The distribution of trace elements in Group IIAB iron meteorites resembles their distribution in some Carboniferous chondrites and enstatite chondrites, suggesting that Group IIAB iron meteorites originate from a single parent body. Group IIC Group IIC iron meteorites include the finest-grained octahedrites with kamasite bands less than 0.2 mm wide. The so-called “filling” plessite, a product of a particularly fine synthesis of taenite and kamasite, also found in other octahedrites in a transitional form between taenite and kamasite, is the basis of the mineral composition of iron meteorites of group IIC. Group IID Meteorites of this group occupy a middle position on the transition to fine-grained octahedrites, characterized by a similar distribution of trace elements and a very high content of gallium and germanium. Most Group IID meteorites contain numerous inclusions of the iron-nickel phosphate schreibersite, an extremely hard mineral that often makes Group IID iron meteorites difficult to cut. Group IIE Structurally, Group IIE iron meteorites belong to the class of medium-grained octahedrites and often contain numerous inclusions of various iron-rich silicates. Moreover, unlike meteorites of group IAB, silicate inclusions do not have the form of differentiated fragments, but of solidified, often clearly defined drops, which give iron meteorites of group IIE optical attractiveness. Chemically, group IIE meteorites are closely related to H-chondrites; it is possible that both groups of meteorites originate from the same parent body. Group IIF This small group includes plessite octahedrites and ataxites, which have high content nickel, as well as a very high content of trace elements such as germanium and gallium. There is a certain chemical similarity with both the pallasites of the Eagle group and the Carboniferous chondrites of the CO and CV groups. It is possible that the pallasites of the Eagle group originate from the same parent body. Group IIIAB After group IAB, the most numerous group of iron meteorites is group IIIAB. Structurally, they belong to coarse and medium-grained octahedrites. Sometimes inclusions of troilite and graphite are found in these meteorites, while silicate inclusions are extremely rare. However, there are similarities with the main group pallasites, and both groups are now believed to be descended from the same parent body.
Group IIICD Structurally, group IIICD meteorites are the finest-grained octahedrites and ataxites, and in chemical composition they are closely related to group IAB meteorites. Like the latter, Group IIICD iron meteorites often contain silicate inclusions, and both groups are now thought to originate from the same parent body. As a result, they also have similarities with winonaites, rare group primitive achondrites. Typical of group IIICD iron meteorites is the presence of the rare mineral hexonite (Fe,Ni) 23 C 6, which is present exclusively in meteorites. Group IIIE Structurally and chemically, group IIIE iron meteorites are very similar to group IIIAB meteorites, differing from them in the unique distribution of trace elements and typical hexonite inclusions, which makes them similar to group IIICD meteorites. Therefore, it is not entirely clear whether they form an independent group descending from a separate parent body. Perhaps further research will answer this question. Group IIIF Structurally, this small group includes coarse to fine-grained octahedrites, but is distinguished from other iron meteorites by both its relatively low nickel content and the very low abundance and unique distribution of certain trace elements. Group IVA Structurally, group IVA meteorites belong to the class of fine-grained octahedrites and are distinguished by a unique distribution of trace elements. They have inclusions of troilite and graphite, while silicate inclusions are extremely rare. The only notable exception is the anomalous Steinbach meteorite, a historical German find, as it is almost half red-brown pyroxene in a type IVA iron-nickel matrix. Whether it is a product of an impact on an IVA parent body or a relative of pallasites and therefore a stony-iron meteorite is currently being vigorously debated. Group IVB
All iron meteorites of group IVB have a high nickel content (about 17%) and structurally belong to the class of ataxites. However, when observed under a microscope, one can notice that they do not consist of pure taenite, but rather have a plessite nature, i.e. formed due to the fine synthesis of kamacite and taenite. A typical example of group IVB meteorites is Goba from Namibia, the largest meteorite on Earth. UNGR Group This abbreviation, meaning “out-of-group,” refers to all meteorites that cannot be classified into the above-mentioned chemical groups. Although researchers currently classify these meteorites into twenty different small groups, for a new meteorite group to be recognized, it generally requires at least five meteorites to be included, as established by the requirements of the Meteorite Society's International Nomenclature Committee. The presence of this requirement prevents the hasty recognition of new groups, which later turn out to be only an offshoot of another group.
Iron, ironstone and achondrites. Iron meteorites.
Most iron meteorites, when sawed, polished, and acid-etched, exhibit a lattice-like pattern on the treated surfaces called Widmanstätten figures. This pattern occurs when, as the temperature decreases, two crystallizing minerals can no longer completely mix in solid form.
Suppose the atoms of two elements are similar but not identical (such as the atoms of iron and nickel), and therefore they each form crystal lattices slightly different from each other. At high temperature these two types of atoms can freely exchange in the crystal due to loose packing in the expanded crystal lattice. But as the temperature decreases, the difference between the atoms different types becomes noticeable.
There comes a point when the energy of the entire system can be reduced by distributing the atoms into two different lattices with a predominance of different elements, even if this does not result in a good coincidence of the boundaries at the junctions of the lattices.
To keep the mismatch to a minimum, new lattices grow in the mother lattice along the prevailing directions in the form of plates of exsolution (decay of the solid solution). A familiar example to petrologists is the pertitic structure in alkali feldspars.
Consider a mixture containing, say, 10% nickel in iron, at an initial temperature of 1000°C
Consider a mixture containing, say, 10% nickel in iron, at an initial temperature of 1000°C. At this temperature, both elements are completely mixed in solid solution, but when the temperature drops to point B, this is no longer the case. Below point B, inside the taenite lattice (y-phase of nickel iron), kamacite (a-phase of nickel iron) is formed, having the composition Bx. Further cooling to point C increases the dissimilarity of the two crystal lattices, although the proportions of Ci and C2 should be such that the overall composition contains 10% Ni and 90% Fe.
Kamacite forms within taenite along certain planes
Kamacite forms within taenite along certain planes corresponding to the surfaces of the octahedron; therefore, the name "octahedrite" is sometimes used for such meteorites. The surfaces of the octahedron (consisting of two pyramids adjacent at the bases) belong to only four planes, since the opposite faces are parallel, and on random sections through the crystal various Widmanstätt figures appear, similar, however, to the patterns that are visible in Fig. 
For the exsolution plates to fully develop, it is necessary that the atoms have sufficient time to redistribute by diffusion in the solid state, and since diffusion slows down as the temperature decreases, the composition of the crystal lattices ends up being “frozen.” The faster the cooling occurs, the higher the diffusion inhibition temperature. A detailed study of the composition of exsolution plates in a number of iron metals gives values for the cooling rate of the order of 1-10°C per million years.
This slow cooling is best explained by assuming that each such meteorite was part of a hot body that cooled slowly due to its size and also due to the insulating effect of the silicate “mantle.” Calculations show that the diameter of such a body should be on the order of several hundred kilometers, which is comparable to the size of large asteroids.
