

mineral cabinet in 1772. Later the whole piece was cut to two parts which
you can see on the exhibit together with the natural size gypsum
model of uncut piece.
The name "Pallas Iron" was given to that meteorite by academician E.F.Chladni (1756-1794). He founded the piece turned out to be an olivine and nickel iron mixture. The mineralogical composition of the piece was very different compare to earth stones so E.F.Chladni suggested the piece came from the sky. Studying that stone E.F.Chladni made a significant contribution to the meteoritic science. After him all meteorites with the composition and structure similar to "Pallasovo zheleso" (containing about equal amounts of olivine and nickel-iron) were given the name "pallasites".
suggestions
they are formed from molten in impact moment rocks ejected into the atmosphere.
That explains
The geography of Sikhote-Alin' meteoritic
shower falling and it's material represented in a
separate
case. This is the biggest meteoritic shower the people ever directly observed.
Although this is not the biggest among known. For
example in 30-es years of lust century the iron masses of Gibeon
meteoritic shower were found in South Africa. This event supposedly had
happened about 20000 years ago. Many hundred tons of iron fall down at
that time. By weight of pieces found Gibeon more than Sikhote-Alin' as
minimum in few times.
The falling of Sikhote-Alin' took place by February
12, 1947 in west part Sikhote-Alin mountain range. Approximately about
100 ton fell down. The number of separate pieces - couple hundred thousands.
The bigger pieces caused 24 craters with diameter to 30 meters and a number
of smaller holes. The biggest piece found (1745 kg) on the podium in museum
meteorite section.
| The biggest Sikhote-Alin individual piece 1745 kg. | Smaller drops of Sikhote-Alin's shower. |
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The studying mineralogy of
the material from space revealed the fact of close similarity mineral
species
and associations of deep parts of the Earth. Many
mineral species, originally discovered in meteorites were found soon on
the Earth. Just a few species exclusively known for the meteorites. The
meteorite mineralogy relatively poor compare to the Earth. It's known less
than 200 mineral species in space matter and more than 4000 species
currently known on the Earth.
The most common meteorite mineral is the native iron alloys - kamasite, taenite and others. Among silicates more common olivine and pyroxenes.
For example Sikhote-Alin' meteorite mostly consist of
kamasite (cubic FeNi) with small quantity of taenite (cubic NiFe). Accessory
minerals are schreibersite (Fe,Ni)3P, troilite FeS, chromite
FeCr2O4, daubreelite FeCr2S4,
cogenite (Fe,Ni,Co)3C. Silicates found as rare inclusions. The
chemical composition of this meteorite in bulk is(%): Fe-93.32; Ni-5.71;
Co-0.48; Cu - 0.011; P - 0.28. In the meteorite Noviy Urey the diamond
is found . In meteorite Staroe Boriskino were found water containing silicates
of chlorite and serpentine groups..
Depending on mineral composition the meteorites divided to iron meteorites, stony-iron meteorites and stone meteorites. The subdivisions in those classes are defined by meteorite structures or minerals.
The structure of iron meteorites could be highlighted
using the etching of meteorite polished surfaces in strong acids. After
the etching the Widmanstatten (after the name of it's first describer)
figures can appear. According the 3D shape of the developed plates
the iron meteorites dividing to octahedrites, hexahedrites and ataxites
(fail to show any obvious structure). The farther subdivisions are according
the size those plates (lamellas).
For example Sikhote-Alin is a coarse structured octahedrite, and
Gibeon, Namibia is a fine octahedrite.
.
On the exhibit you can find relatively big pieces
of Gibeon (left on the photo- 327 kg) and also cut, polished and etched
specimens. Another octahedrite Syromolotovo (217 kg) fell down in
Russia in 1873. (right on photo)
A big cut plate of octahedrite Mundrabilla
(Western Australia) was presented to collection in 1966 by professor
P.Ramdor.
Among hexahedrites on the exhibit is Broumov fell down
in 1847 in Czech. One of the most
beautiful
iron meteorites is kamasite hexahedrite
Boguslavka. It's Russian fall in 1916 represented
in museum by the piece broken during the fall on two parts 198.6
and 58.1 kg. Those parts are the fragments of one crystal of kamasite !
. It's belonging to hexahedrites was proved on other samples of this fall.
The stony-iron meteorites divided according
mineral composition to:
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| Pallasites | taenite, olivine |
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| Mesosiderites | taenite, pyroxen, plagioclase |
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| Lodranites | taenite, pyroxen, olivine |
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The most usual minerals in stone meteorites are olivine
and pyroxenes. The common accessory minerals are plagioclases, NiFe alloys.
Quartz, amphiboles, micas, serpentine, chlorite, troilite are rare minerals.
The maine subdivision of stone meteorites is according
to it's structure to chondrites and achondrites.
Chondrites are the most common type.
It's name came from small spherical inclusions called chondrules. This
texture not found in terrestrial rocks. The chondrules's average size is
1 mm, rarely up to 5-7 mm. Chondrules different in structure but have the
same mineral constitution as surrounding masses. The genesis of chondrules
is unclear.
By mineral composition the maine chondrite's subdivisions
are ordinary (olivine-bronsite-hypersten),
enstatite chondrites and carboniferous chondrites.
Achondrites as it's clear from their
name have different texture. As it's proposed achondrites formed by melting
and recrystalisation of parent chondritic bodies. The structure of achondrites
more close to terrestrial's rocks. There are a number of subdivisions of
achondrites according it's mineralogy.
The
short excurs to meteorite classification had to be done since the rest
of the museum meteorite exhibit in show cases and podiums arranged according
it's classes and in chronological (the year of the fall) order inside classes.
Among
meteorites on exhibit are the main masses of many Russian falls and a number
of meteorites remarkable by it's structure and composition (Nechaevo, Shassin'i);
by it's size and shape (Kashin,
Kainsaz ); by the time of the fall
(the part of Ensisheim chondrite first recorded fall in 1492)
.
There are represented valuable parts of meteoritic showers Kunashak, Chinge and others.
Click the active areas on the photo to see showcases in more details or go to the meteorite part of image gallery to see the images of most interesting specimens.
The big scheme of the Earth's structure hanged above the
showcases to remind that although the meteorites falling from the sky they
are helping to study internal Earth's zones. As it's supposed to be the
iron meteorites are the parts of the planets core , stony-irons and chondrites
are respectively the parts of lower and upper mantle of the planets and
achondrites - the planet's crust.
Indeed the meteorites are the most old matter we can met. The age of most iron meteorites is about 4.5 milliard years. They are as minimum twice older of the any most ancient earth rock. Some of meteorites may be even older (to 7 milliard years). They may e represent the other planet systems.
Finally recent contributions in finding organic compounds in meteorites are giving the base to suggest the meteorites could be the source of life on the earth.