Roughly spherical aggregate of coarse crystals formed from the rapid cooling and solidification of a melt at  ~1400 ° C. Large numbers of chondrules are found in all chondrites except for the CI group of carbonaceous chondrites. Chondrules are typically 0.5-2 mm in diameter and are usually composed of olivine and pyroxene, with smaller amounts of glass and Ni-Fe metal. Chondrules can sometimes exceed 10 mm and are considered megachondrules or macrochondrules. Together with CAIs, which predate chondrules by ~2-3 Ma, they are among the oldest objects in the Solar System with an age of ~4.56 Ga. They formed when “dust balls” were shock heated to very high temperatures, became molten, and resolidified as  tiny droplets. Type I chondrules are FeO-poor; whereas, Type II are FeO-rich. Other chondrules are cryptocrystalline, or show barred or radial textures. Chondrules will also have fine-grained matrix rims and/or coarse-grained igneous rims as well as metal rims suggesting complex formation histories.

Some or all content above used with permission from J. H. Wittke.