Abstract
We could find matrix olivine particles with various morphologies and surface microtopographs in primitive meteorites like Allende chondrite. We have experimentally tried to reproduce the morphologies and surface microtopographs of the matrix olivine with condensation experiments.
A 100W of CO2 laser was employed to heat a forsterite polycrytalline spherule for melting in <100 sec. The condensed forsterite crystals were characterized by TEM, FE-SEM, AFM and DICM.
As the temperature decreased and thus the supersaturation of the vapor increased, the morphology of forsterite changed from a bulky type to a platy type, then to a columnar needle shape, and finally to a droplet type. Various 2-dimentional islands with the step height of 0.3 nm-few nm were observed: rectangular growth islands with a smooth-edge step, islands with a rough-edge step, and a droplet type. These external and surface morphologies have been compared with natural matrix olivine. In addition, we could find matrix olivine particles with various surface microtopographs, which show that the particle formed at 1800 K followed by rapid cooling in ~10 s down to 1000 K.
