Melilite
Melilite is a calcium-aluminium-magnesium silicate that is a main mineral of many CAIs.
Melilite is a silicate series between gehlenite, which is calcium-aluminium-rich, and åkermanite, which is calcium-magnesium-rich. It forms at high temperatures and is rare in ordinary Earth rocks.
In meteorites, melilite is a major component of many calcium-aluminium-rich inclusions, especially the large Type A and Type B inclusions in CV chondrites such as Allende. These white blobs, sometimes centimetres across, formed or melted at about 1,400 °C or more within the first few hundred thousand years of the Solar System. Melilite crystals in them are often zoned, recording how the inclusion cooled.
Melilite alters easily when fluids pass through, turning into secondary minerals such as nepheline and sodalite. That makes it a sensitive witness to what happened later on the parent asteroid. Under the microscope its crystals typically show low, distinctive interference colours, which help petrologists recognise it.
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