NEW AND IMPORTANT METEORITE - POSSIBLY THE ONLY KNOWN MATERIAL FROM THE PLANET MERCURY
NWA 7325 - Achondrite (ungrouped)
Bir El Abbas, southern Morocco
This is the very first meteorite believed to be from the planet Mercury. It was discovered in a strewn field of very fresh, dark greenish stones totaling approximately 995 grams, in southern Morocco in early 2012, and first purchased in the market at Erfoud in April of that year. Comparing data from the Messenger spacecraft, Professor Anthony Irving of the University of Washington determined that this meteorite's composition is consistent with that of the planet in our solar system closest to the Sun, Mercury, which Messenger has been orbiting since early 2011. Lead isotopes in the rock were tested for the radioactive decay of uranium by the University of Canberra, Australia, and it was determined that the age of the meteorite is approximately 4.56 billion years. This places it very close to the formation of the planet Mercury itself, hence it may also have come from a smaller, Mercury-like proto-planet. Nonetheless, specimens like the ALH84001 from Mars are considered to be as old, if not older, and despite the proximity of Mercury to the Sun's gravitational pull, it has been calculated that detritus thrown up by rocks hitting the planet would be propelled fast enough (faster than 9 km per second) to break free not only of the atmosphere but also of the Sun's gravitational field, and that 2 to 5% of such matter could reach Earth within 30 million years.

NWA 7325 is classified as a mafic achondrite, rich in magnesium but containing very little iron. The combination of highly magnesian mafic silicates, and highly calcic plagioclase with chromium-bearing sulfides (a large amount of pyroxene) is unique among achondrites; present too are the very rare eskolaite, kamacite, taenite, and sparse ferrochromite.

This is one of the complete nuggets from that unprecedented find, of aesthetic skewed pyramidal form, with a wonderfully textured fusion crust, shading from dark green-yellow to sandy red, with distinct ridges suggesting a consistent orientation during its violent, fiery descent through the atmosphere. This feature is unusual enough and here produces a highly aesthetic specimen, but it is the supposed origin that makes this such an important, rare, and highly collectible meteorite, approximately 1 5/16 x 1 1/4 x 15/16 inches, weighing approximately 22.5 grams.