When the planets of our solar system aggregated from the primordial dust and ice swirling in a disc around the sun, some crazy things happened. We are used to the relatively stable result, 4.6 billion years later, but in the early days, some planetoids collided cataclysmically; others were flung out of our solar system entirely, to the lifeless void of deep space.
These dense iron meteorites contain the molten metal cores of some planetary body that ended in a mighty kaboom. We know it was big because a molten iron core appears when a planetoid is big enough to have enough gravity to fractionate the elements of the periodic table, with the heavier iron-loving elements migrating to the core and a different subset of the periodic table (e.g., Si, Al, Ca, Na, Mg) constituting the outer mantle and crust. We have never drilled to the molten core of Earth, or even deep into our mantle, but these remnants of planets past are representative of what we would expect to find in the Earth’s core and mantle.
Two big iron meteorites arrived this week, this 45 lb Sericho Pallasite from Kenya and a 127 lb heavy metal barbell from Argentina (Campo del Cielo). Pallasites are an incredible potpourri of shattered mantle in a dollop of molten metal core. They can only form in space where the absence of gravity allows the lighter gemstones to remain scattered throughout the heavy metal matrix (on Earth, they would segregate by density). Those crystal gems are olivine (peridot) and this example shows an array of colors from honey to burnt orange to dark green.
The Campo from Argentina is a deeper core sample, so to speak, of pure molten core of a destroyed planetoid. If we were to look at the metal crystalline patterns inside, we would see something beautiful, an interwoven 3D nest of interlocking shards, a metal crystallization that also could not be made on Earth, but for a different reason: they have to cool very, very slowly, over 10 million years! In the insulating vacuum of space, the motel metal cools slowly as it radiates heat (no conduction or convection).
If this all sounds like a rare event, it is. 2% of meteorites in the Met Bull are irons, and only 0.2% are Pallasites, the most visually beautiful of space rocks, IMHO.
When an iron meteorite is forged into a tool or weapon, the extraterrestrial crystal patterns remain, but become stretched and distorted. The patterns usually cannot be fully eliminated by blacksmithing, even through extensive working. When a knife or tool is forged from meteoric iron and then polished, the patterns appear in the surface of the metal. In ancient times before the invention of steel, these iron-nickel alloys were like advanced alien technology, and probably were the origin of folkloric beliefs about magic swords and vorpal blades. Even King Tut was buried with his meteorite dagger.
There is much going on in this Sericho Pallasite — a meteoritic medley. Transluscent olivine gems across the color spectrum. And the metal matrix has large Farringtonite inclusions (beige) and Chromite (flat black, bottom center). Rounded upper lip is shaped from oriented entry through the Earth’s atmosphere. 45 lbs, 31x25x15cm.
Based on isotope analysis at ETH Zürich, this meteorite spent the last 130-160 million years free floating in space before intersecting Earth’s orbit.
From the Met Bull for Sericho: “In 2016, two brothers were searching for their camels and came across several large, dense stones south of Sericho, Kenya. There are no rocks in this area, so they decided they were meteorites. They spent several weeks collecting them with engine hoists and moving them to their homes in Habaswein. The masses had been known to camel-herders for decades prior. One village elder said that as a child, he and his brothers would play on top of the stones. In early January 2017, Michael Farmer received an email showing a photo of a ‘giant pallasite’. He traveled to Nairobi and purchased this stone.”
^ baby Luna as a hand model! 😉
Chromite in flat black
The metal crystal pattern 
Leave a Reply to jurvetson Cancel reply