Calcium–aluminium-rich inclusion

CAIs consist of minerals that are among the first solids condensed from the cooling protoplanetary disk.

They are thought to have formed as fine-grained condensates from a high temperature (>1300 K) gas that existed in the protoplanetary disk at early stages of Solar System formations.

The most common and characteristic minerals in CAIs include anorthite, melilite, perovskite, aluminous spinel, hibonite, calcic pyroxene, and forsterite-rich olivine.

[1][2] They yield a weighted mean age of 4567.30 ± 0.16 Myr, which is often interpreted as representing the beginning of the formation of the planetary system (so-called ‘CAI time-zero).

It is of note that all four Pb-Pb dated CAIs come from the same group of meteorite (CV chondrites).