IIE irons
Irons full of silicate fragments, possibly from asteroid Hebe.
- Classification
- Iron meteorites › IIE irons
- Share of witnessed falls
- about 0.2%
- In our catalogue
- 22 meteorites, 2 seen to fall
- Heaviest
- Miles, 265 kg
- Earliest recorded fall
- Garhi Yasin, 1917
- Most recent fall
- Kavarpura, 2006
IIE irons are octahedrites of varying coarseness that often contain silicate inclusions, some chondritic and some melted. Their oxygen isotopes are close to H chondrites, and they may come from pools of impact melt on the H chondrite parent body, possibly the asteroid 6 Hebe.
Mineralogy and chemistry
IIE irons contain about 7.5% to 10% nickel and range from coarse to fine octahedrites, some with unusual structures. Many contain silicate inclusions of two very different kinds. Some, as in Netschaëvo, are almost unmelted chondritic rock with relic chondrules, resembling H chondrites. Others, as in Colomera, Kodaikanal, Miles and Weekeroo Station, are melted and differentiated, rich in silica, sodium and potassium, with minerals such as sanidine feldspar and glass.
Their trace elements scatter rather than following a single crystallisation trend, so IIE is classed as non-magmatic.
Parent body and formation
Oxygen isotopes of IIE silicates lie close to those of H chondrites, and many researchers think IIE irons formed on the H chondrite parent body, or one very like it, when impacts created pools of molten metal and silicate near its surface. The asteroid 6 Hebe, a candidate H chondrite source, has been suggested. Some IIE irons, such as Netschaëvo, record early formation about 4.5 billion years ago, while others, such as Kodaikanal, have silicates reset about 3.7 billion years ago, suggesting several impacts over a long period. Other researchers argue that the parent body partly melted and formed a small core, so the debate continues.
Abundance and famous examples
IIE is a modest group of a couple of dozen members. Garhi Yasin, which fell in present-day Pakistan in 1917, is the only fall, with only about 380 g recovered. Netschaëvo, found in the Tula region of Russia in 1846, contains chondritic clasts with visible chondrules. Colomera, found in southern Spain in 1912 (about 134 kg), contains crystals of potassium feldspar. Miles, found in Queensland in 1992, is rich in silicate inclusions. Weekeroo Station from South Australia and Kodaikanal from India are other well-known members.
How to recognise one
Cut faces of many IIE irons show rounded or angular inclusions of grey or greenish silicate in metal, some up to several centimetres. The metal etches to an octahedrite pattern. They are heavy and magnetic. Telling them from IAB irons with silicates requires chemical analysis and oxygen isotopes.
Famous examples
- Weekeroo Station Iron, IIE-an, Australia, 1924 · 94.2 kg
- Netschaëvo Iron, IIE-an, Russia, 1846 · 250 kg
- Colomera Iron, IIE, Spain, 1912 · 134 kg
- Kodaikanal Iron, IIE, India, 1898 · 15.9 kg
- Miles Iron, IIE, Australia, 1992 · 265 kg
- Garhi Yasin Iron, IIE, Pakistan, 1917 · 380 g
- Elga Iron, IIE, Russia, 1959 · 28.8 kg
Related groups
- H chondrites High-iron ordinary chondrites: about a third of all meteorites seen to fall.
- IAB irons Irons with stony inclusions, from a partly melted asteroid. Canyon Diablo and Campo del Cielo.
- Ordinary chondrites The everyday meteorite: four in every five falls. Three groups, H, L and LL, from at least three asteroids.
- Iron meteorites Almost pure iron-nickel metal, mostly from the cores of asteroids that melted and were later shattered.
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