EL chondrites
Low-iron enstatite chondrites.
- Classification
- Stony meteorites › Chondrites › Enstatite chondrites › EL chondrites
- Share of witnessed falls
- about 0.8%
- In our catalogue
- 120 meteorites, 8 seen to fall
- Heaviest
- Northwest Africa 2965, 100 kg
- Earliest recorded fall
- Pillistfer, 1863
- Most recent fall
- Neuschwanstein, 2002
EL chondrites have less metal than EH chondrites and contain alabandite, a manganese sulphide, instead of niningerite. Most are strongly heated, petrologic type 6.
Mineralogy and chemistry
EL chondrites contain about 25% total iron by weight, less than EH chondrites, and their kamacite holds about 1% silicon. Their characteristic sulphide is alabandite, a manganese-rich sulphide, rather than the niningerite of EH chondrites. Chondrules are larger, around 0.6 mm, though in the common, strongly heated type 6 rocks they are blurred by recrystallisation.
Like EH chondrites they are made largely of iron-free enstatite and contain oldhamite, daubréelite and other minerals of very reduced conditions. Sodium-rich plagioclase becomes visible in the more heated examples. Oxygen isotopes lie on the terrestrial line.
Parent body and formation
Most EL chondrites are type 6, and many show signs of having been heated close to melting or partly melted by impacts, followed by slow cooling. That suggests their parent body was larger or reached higher temperatures than the EH body. Unequilibrated EL3 chondrites are rare finds; Antarctic examples such as MacAlpine Hills 88136 keep sharp-edged chondrules and show that EL material began as typical chondritic rock before it was heated. Some scientists see the EL parent body as related to the aubrites, which formed from similar material that melted completely, though the two do not seem to share a parent. Fragments of EL rock were found among the Almahata Sitta stones that fell in Sudan in 2008, showing that pieces of different bodies had been mixed together on one asteroid.
Abundance and famous examples
EL chondrites are about 0.8% of witnessed falls. There is no type specimen, as the group is defined by chemistry. Hvittis, which fell in Finland in 1901 (about 14 kg), is a classic EL6. Pillistfer, Estonia, 1863; Khairpur, Pakistan, 1873; Daniel's Kuil, South Africa, 1868; and Eagle, Nebraska, 1947, are other well-documented falls.
Research highlights
Because EL chondrites were so strongly heated, their minerals reached chemical balance, and they are used to study how sulphides, metal and silicates share elements under very reduced conditions. Their nearly iron-free silicates give them a pale, featureless spectrum, quite unlike ordinary chondrites, which is why astronomers look for their parent bodies among the bright E-type and some of the M-type asteroids.
EL chondrites also contain the nitride sinoite and silicon-bearing metal in amounts that record how much oxygen was available, allowing scientists to compare them directly with the aubrites, their melted relatives.
How to recognise one
An EL is a grey, recrystallised stone with plenty of metal, strongly magnetic and heavy, often with few visible chondrules. It looks much like an H chondrite to the eye. Only analysis showing iron-free pyroxene, silicon in the metal and alabandite confirms the group. Like EH chondrites, they rust quickly in damp air, and their calcium sulphide breaks down on contact with water, so the best-preserved specimens are fresh falls kept in dry cabinets and finds from the cold, dry ice of Antarctica.
Famous examples
- Hvittis EL6, Finland, 1901 · 14 kg
- Eagle EL6, United States, 1947 · 10 kg
- Pillistfer EL6, Estonia, 1863 · 23.25 kg
- Khairpur EL6, Pakistan, 1873 · 13.6 kg
- Daniel's Kuil EL6, South Africa, 1868 · 1.06 kg
Related groups
- EH chondrites High-iron enstatite chondrites.
- Enstatite chondrites Chondrites formed with almost no oxygen to spare, full of rare minerals unknown on Earth's surface.
- Aubrites Pale, almost iron-free rocks made of enstatite, from an extremely oxygen-poor world.
Photos shared under Creative Commons licences (Wikimedia Commons).