NWA 7831 Olivine DIogenite — 5x Macro #3

3 responses to “NWA 7831 Olivine DIogenite — 5x Macro #3”

1. 

   jurvetson

   Jan 23, 2021 at 8:56 pm

   full stone

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2. 

   jurvetson

   Apr 30, 2021 at 11:33 pm

   Diogenite comes from deep in the mantle of Vesta, We have never drilled that deep on Earth, but it might look somewhat similar. New work on exposed mantle in Maryland give us a sense of what it looks like. From National Geographic:

   "While this layer of rock is usually found between the planet’s crust and core, a segment peeks out of the scrubby Maryland forest, offering scientists a rare chance to study Earth’s innards up close. Even more intriguing, the rock’s unusual chemical makeup suggests that this piece of mantle, along with chunks of lower crust scattered around Baltimore, was once part of the seafloor of a now-vanished ocean.
   Over the roughly 490 million years since their formation, these hunks of Earth were smashed by shifting tectonic plates and broiled by searing hot fluids rushing through cracks, altering both their composition and sheen. Mantle rock is generally full of sparkly green crystals of the mineral olivine, but the rock in my hand was surprisingly unremarkable to look at: mottled yellow-brown stone occasionally flecked with black.
   “Those rocks have had a tough life,” says George Guice, a mineralogist at the Smithsonian’s National Museum of Natural History.

   THE LURE OF GREEN SPARKLE
   Guice has long chased after sparkly green rocks, known to geologists as ultramafic. They’re rich in magnesium and make up the majority of our planet as the mantle. But pieces of the mantle are rare at the surface, and ultramafic rocks can form in several different ways, including in large crystallizing magma chambers. They’re also devilishly difficult to study.

   Ultramafic rocks form deep underground at high temperatures and pressures, so their minerals are not stable near Earth’s surface. In this shallow environment, they’re often exposed to hot fluids rushing through cracks, transforming their mineral makeup, as seen in the rocks strewn around Baltimore. Understanding the rock’s history through these changes, Guice says, is like looking through thick fog."

   Meteorites offer a preserved time capsule from these depths, albeit from an alien world.

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3. 

   jurvetson

   Apr 14, 2024 at 6:42 pm

   New research related to the anorthite contained in some rare Vestian meteorites, like mine here: Meteorite suggests asteroid Vesta may once have had magma lake just like the early moon, say Chinese scientists: "The researchers said that while Vesta is much smaller than the moon and other planets, the “planetary embryo” has a similar evolutionary history to the moon. Anorthosites are formed when magma oceans solidify and the only ones that have previously been found have come from the Earth or the moon."

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