Gehlenite
The aluminium-rich end of the melilite series, typical of the oldest inclusions in chondrites.
Key facts
- Formula
- Ca2Al(AlSi)O7
- Family
- Silicates
- Crystal system
- Tetragonal
What it is
Gehlenite is the aluminium-rich member of the melilite group, a family of calcium silicates in which pairs of silicon–oxygen groups are joined into sheets. It forms a series with åkermanite, the magnesium-rich member. It is named after the German chemist Adolf Gehlen.
Where it is found
It is a major mineral of type A calcium-aluminium-rich inclusions in CV chondrites such as Allende and Vigarano, where it condensed from or crystallised in hot gas around the young Sun. Melilite in inclusions is often zoned from gehlenite in the core towards åkermanite at the rim.
How it is recognised
Under the microscope it shows low, slightly blue-grey interference colours. Its exact place in the series is measured with the microprobe.
Did you know?
Gehlenite is also a component of some slags and cements.
Melilite is one of the first silicates expected to condense from cooling solar gas.