Micrometeorites, Cap Prudhomme

Unmelted micrometeorites (MMs) Characterized by a thin outer layer of platy magnetite containing not only iron but also magnesium, aluminum, silicon, and manganese. 

Scoriaceous MMs Composed of highly vesicular glass with varying amounts of residual anhydrous minerals. 

Cosmic spherules Composed of quench-textured silicate glass with/without vesicles and residual anhydrous minerals. 

Meteorite-ablation spherules Form when the molten layer of stony meteoroids passing through the terrestrial atmosphere is stripped off and congeals into glassy spherules that fall to the surface of the Earth. 

Cosmic spherules that formed by melting of micrometeorites can be distinguished from ablation spherules of stony meteorites by the observed concentrations of cosmogenic Be, Al, and Mn they contain. Nishiizumi et al. (1991) measured the concentrations of Al and Be of a large number of cosmic spherules from deep-sea sediment and from the meltwater lakes on the Greenland ice sheet. The evidence indicated that the spherules had been exposed to galactic cosmic rays and to the solar wind for more than one hundred thousand, but less than 10 million, years while they revolved 

---