A new acquisition for the budding rock collection – a slice of the Sericho pallasite! This beautiful specimen was once part of an asteroid’s core–mantle boundary, and similar stony iron meteorites are some of our best proxies for the Earth’s own interior. Here you can see megacrysts of olivine in gemmy green and orange, suspended in an iron–nickel groundmass. The olivine has characteristic curvilinear fractures, but also several sub–parallel shock fractures, possibly formed on impact. The free metal groundmass has apparent mm–scale banding, a characteristic of octahedrite Widmanstatten patterns (apparent I say because Widmanstatten patterns can only be seen after acid etching, and I don’t know how the sample was prepared – in the case that this was an over–enthused interpretation, I offer the lesser alternative of mechanical scratches from slicing).
Pallasites are thought to have formed during magma ocean differentiation on larger asteroids. The heat generated by short lived radionuclides and high interior pressures leads to melting and density segregation into an iron core and a silicate magma ocean. As this too cools, denser crystal–rich melts will settle as olivine cumulates, aided by convection and crustal foundering. At the core–mantle interface, the molten metal of the core is thus mixed with the olivine cumulates, resulting in stony iron formation. Small asteroidal bodies cannot stay hot for long, and so will ‘freeze’ at some point in their early histories. Impacts can break up these solidified asteroids and reassemble them into rubble piles – or they can send them hurtling our way, which is what happened with Sericho, and why we can observe what we can today!
In the western portion of the proximal ejecta of Bakhuysen Crater, a geologic contact between two units is visible. Mapping of these units may give insight into the emplacement of ejecta for large basin impact structures on Mars. Small-scale mounds near one such contact may be hydrothermal in origin.
Images are less than 5 km across.
date: 17 November 2015
altitude: 256 km
For about seven-eights of the Earth's history, its oceans were extremely rich in sulfides. This would have prevented animals and plants from surviving in 70% of the planet. But it was a great habitat for photosynthetic bacteria that require sulfides and sunlight to live. Known as purple and green sulfur bacteria (because those are the two colors it comes in) these single-celled microbes can only live in environments where they simultaneously have access to sulfides and sunlight.
That they thrived in the sulfide-rich ocean has been confirmed with the finding of fossilized pigments of purple sulfur bacteria in 1.6 billion-year-old rocks from the McArthur Basin in Northern Australia.
So I wanted to know what kind of crystal could go in a wizard staff, right? so I googled “big crystal,” as one does, and got an Etsy ad for This
And as you all know I Am currently taking a geology class, so I am probably more emotionally invested in minerals than usual. But that is...very obviously not a natural crystal.
So I did some looking around on Etsy.
Now, these shops all seem to advertise to the “witchy”/“spiritual healing” type of person. And there are a lot of them. Crystals are a Big Thing on Etsy. And ALMOST ALL of them are obviously artificially cut into the same sort of prism with a triangular pyramid top, regardless of the actual sort of crystal it is supposed to be.
Even like, fucking, obsidian. Obsidian is volcanic glass, it doesn’t form crystals at all, it is not a crystal
I’m not throwing any shade at people who are into crystals for like witchy reasons, but it really seems like if crystals are spiritually important to you, you should know what a crystal is...right...?
We should start referring to lab-grown gemstones as “artisanal”. It’s not fake, it’s hand crafted. Who wants a rock that someone just pried out of the dirt? What do you think I am, some sort of peasant?