Inclusions, enriched in the rare earths and the other elements mentioned in the definition of refractory, which are identified in rocks petrographically because of their mineralogy, which is dominated by Ca-, Al-, and Ti-rich phases. This is why these inclusions are often referred to as Ca-, Al-rich inclusions, or "CAIs. " Most refractory inclusions contain the minerals spinel and melilite and/or hibonite.