Meteorite specialists have identified several kinds of chondrules, classifying them on the basis of the types, abundances, shapes, and compositions of the minerals present. Radioactive dating measurements of the ages of chondrules suggest that they formed in the first few million years after the Solar System formed at 4.566 billion years ago. Stony meteorites called chondrites are chock full of chondrules, as shown, above, in the photograph on the left of the Semarkona chondrite. On the right is a closer view of some typical chondrules in the meteorite Tieschitz, as seen through a polarizing microscope. The colors are not the actual colors of the minerals, but are instead interference colors caused by the optical properties of the minerals and the polarized light of the microscope.
Chondrules lack circular gas bubbles.
Such bubbles, called vesicles , are common in volcanic rocks on Earth, and indicate the presence of gases in the magma. Ideas for Chondrule Formation T here are nearly as many ideas about how chondrules formed as there are scientists working on them. Still others think that chondrules formed by impact melting of pre-existing asteroids or planetesimals. Others have suggested widespread volcanism. This glut of hypotheses is a testament to the richness of human imagination.