At first glance this beautiful black aerodynamic particle from space, NMM 3864, may appear to be a barred olivine (BO-type) micrometeorite. However, closer scrutiny reveals two triangular gaps between the crystal bodies and coarse crystallization in the middle. This is typical for porphyritic olivine (PO-type) micrometeorites, which suffer a slightly lower peak temperature during atmospheric entry.

Because NMM 3864 appears to have characteristics of both barred olivine and porphyritic olivine micrometeorites, I think it’s safe to classify this fresh cosmic gem as a transitional form between the two types.

Measuring approximately 0.3 mm, You can see a circular “crater” in the front of the rock, which is oriented up in this new photo by Jan Braly Kihle and me. Perhaps this crater formed when a metal bead escaped from the micrometeorite during formation? Note also the crack across the top of the stone. This may have been caused by “stress” during recrystallization. Or perhaps someone stepped on it?

If you want to learn more about micrometeorites, we have a NEW website with a blog, books, and a fine art gallery.

If you have questions or a comment, both are appreciated! Please send me your thoughts on Facebook, Instagram, or Twitter and I’ll get back to you asap. Enjoy!

Yours truly,

Jon Larsen