CAIs – Types & Classification with respect to Minerals
Channel: Dominik Hezel
Date: 2023-04-12

Ca,Al-rich inclusions (CAIs) commonly have irregular outlines, can be larger than chondrules and often show a mineralogical zonation from core to rim called ›Wark-Lovering rim‹. The sequence of minerals in such rims correspond to the condensation sequence of refractory minerals and together with the irregular outline of the CAIs indicate that CAIs directly condensed from a cooling gas. In few chondrites, CAIs were re-melted – likely during the chondrule forming process – and now have a similar, roundish appearance as chondrules. CAIs are classified according to various characteristics, one is based on mineralogy of the ternary diagram melilite–Al-rich pyroxene–remaining minerals. 3 types of CAIs (A, B, C) are discriminated in this diagram. Another classification is based on their texture, e.g., fine-grained, coarse-grained, or compact.