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UNCLASSIFIED NWA CHONDRITE METEORITES FOR SALE
Due to their unclassified nature, these meteorites often lack specific designation, making them intriguing specimens for both collectors and researchers. Each piece is unique, showcasing a variety of textures and mineral compositions, often reflecting the conditions of their formation. The exterior typically features a fusion crust—a thin, glassy layer formed during atmospheric entry, while the interior reveals a mix of fine-grained matrix and distinct chondrules.
What Is A Chondrite?
A chondrite is a non-metallic meteorite that has not been modified by differentiation or melting, though some chondrites show aqueous alteration, mostly by deposition of carbonate minerals. This often means that chondrites trend towards smaller sizes, often about the size of a grapefruit. This is because any mass larger than that is more likely to differentiate as it cools at a slower rate. Most importantly, a chondrite contains miniscule silicate-based particles called chondrules, which no other meteorite types have.
Chondrite meteorite from northwestern Africa with good fusion crust.
Chondrites have the same chemical composition as the solar nebula that birthed the sun and our solar system. The only compositional difference is the lack of hydrogen and helium in chondrites. This closely related composition indicates that chondrites' source bodies have remained relatively unchanged (especially in regard to heating and melting) for a very, VERY long time. This also suggests that the source asteroids must have been small enough to prevent differentiation for that entire stretch of time.
What Are Chondrules?
Chondrules are grainy extraterrestrial inclusions that are usually a millimeter or less in size and composed of a variety of metals and minerals that gathered as space droplets in a solar nebula prior to the birth of our solar system. The majority of the components that make up chondrules are silicates, such as olivine and pyroxene. However, chondrules also contain trace metals like iron, aluminum, nickel, and occasionally rare magnesium isotopes. Chondrules are unlike anything on Earth, though the presence of olivine is a good indicator of the age of the grains, because olivine is thought to be one of the oldest Earth minerals, forming in extremely deep pockets within the crust and mantle.
Where To Find Chondrites?
Meteorites fall worldwide, but tend to be found most often in desert regions where they usually stick out like a sore thumb. Many of the available chondrites on the market are sourced from areas in the northern Sahara desert, specifically in Morocco, a country that exports many excellent fossils and Earth minerals. Arizona, New Mexico, and Texas in the United States are also known for meteorite finds. A good amount of meteorites are collected in another often overlooked desert: Antarctica. Most of the meteorites found in Antarctica are enstatite chondrites.
Further Classifications Of Chondrites
Chondrites have three major groups: ordinary, carbonaceous, and enstatite. These categories are allocated based on varying factors, but are primarily related to the presence of certain elements over others. These differences help scientists determine a chondrite's point of origin before it came to Earth.
After a designation in one of these three groups, chondrites are then assigned a number between 1 and 7. Chondrites designated 1 or 2 are known to have chondrules that were aqueously altered, with a 1 meaning the chondrules have been completely changed via the presence of water. A 3 suggests the chondrules haven’t been altered by either thermal or aqueous means. If they were manipulated by heating, a chondrite is assigned a number between 4 and 7, where 4 is minimal metamorphism and 7 being that the chondrules were heated to the point of destruction.
Ordinary - Most of the meteorites on earth are ordinary chondrites. That’s a blanket statement but it is true, more than 90% of collected chondrites are ordinary chondrites. That’s quite extraordinary considering that about 85% of meteorites are chondrites in general. If there are indeed 50,000 confirmed meteorites, 42,500 are chondrites, and roughly 38,250 of them are ordinary chondrites. A staggering number to be sure, but that means there is quite a lot of pre-solar system space dust on Earth.
An ordinary chondrite in cross-section
What constitutes a chondrite being classified as ordinary is the presence of oxidized and volatile elements and low metal content with a high abundance of chondrules. Scientists believe that the parent bodies that spawn ordinary chondrites originated in the asteroid belt between Mars and Jupiter.
There are three types of ordinary chondrites, H, L, and LL. These are determined by the overall iron content of the meteorite. H chondrites have around 20% iron content, L chondrites have about 11%, and LL chondrites contain less than 7% iron by mass. L chondrites are the most abundant of all the ordinary chondrites followed closely by H chondrites, while LL chondrites are exceptionally rare, appearing less than 5% of the time.
Carbonaceous - These meteorites can contain up to 20% water by mass and are considered to be the purest form of a chondrite, remaining almost absolutely unchanged in their journey from birth to splash down on Earth. They have considerable amounts of carbon composition, which takes the form of organic compounds like amino acids. These chondrites show very little evidence of having ever been heated and the internal chondrules are relatively unaltered or were changed by aqueous alteration instead of thermal metamorphosis. Because of their composition, they are believed to have accreted at the furthest reaches of the solar system. The famous Allende meteorite that fell in 1969 is a prime example of a carbonaceous chondrite. C-type chondrites comprise 5% of all chondrites and are designated between 1 and 3 on the alteration scale.
Enstatite - These are easily the rarest of the main types of chondrites. Enstatite (or E-type) chondrites make up less than 2% of all the chondrites that have fallen to earth. They are named after the mineral, enstatite, which accounts for a good portion of their composition. What really sets them apart from other varieties of chondrite is that their iron content presents in a sulfide state or as a solid metal, which suggests there was less oxygen present during formation to bind the metal in silicates and oxides. A low oxygen environment is consistent with areas at the inner edge of our solar system, like Mercury or Venus. It is because of this that Enstatite chondrites are believed to come from the inner solar system within the orbit of the first planet from the sun.
Enstatite chondrite in cross-section.
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