Chondrule

Small amounts of other minerals are often present, including Fe sulfide (troilite), metallic Fe-Ni, oxides such as chromite, and phosphates such as merrillite.

Less common types of chondrules may be dominantly composed of feldspathic material (again either glassy or crystalline), silica, or metallic Fe-Ni and sulfides.

When the pyroxene fibers are coarser, they may appear to radiate from a single nucleation site on the surface, forming a radial or excentroradial texture.

Other observed textural features that are clearly the result of very rapid cooling are dendritic and hopper-shaped olivine grains, and chondrules that are composed entirely of glass.

Some chondrules contain very little iron oxide (FeO), resulting in olivine and pyroxene that are close to forsterite (Mg2SiO4) and enstatite (MgSiO3) in composition.

Proposed heating mechanisms are: Isotope studies indicate a nearby supernova explosion added fresh material to what became the Solar System.

In contrast, the fine grained matrix, in which the chondrules are embedded after their accretion into the chondrites parent body, is assumed to have been condensed directly from the solar nebula.