Donwilhelmsite
A dense calcium aluminium silicate in lunar meteorites, made from shock-melted Moon crust.
Key facts
- Formula
- CaAl4Si2O11
- Family
- High-pressure minerals
- Crystal system
- Hexagonal
- First described
- the lunar meteorite Oued Awlitis 001, 2020
Donwilhelmsite was described in 2020 from the lunar meteorite Oued Awlitis 001, found in Western Sahara. It is named after Don Wilhelms, an American geologist who mapped the Moon for the Apollo programme. It has also been reported from Martian meteorites.
What it is
Donwilhelmsite is a calcium–aluminium silicate with a structure that is stable only at high pressure. It is rich in aluminium because it formed from melted anorthosite, the plagioclase-rich rock of the Moon's highland crust. Experiments suggest that minerals like it could carry calcium and aluminium deep into Earth's mantle when ocean crust sinks.
Where it is found
It was found as tiny needle-shaped crystals in shock-melt veins in Oued Awlitis 001, a feldspathic breccia from the Moon. It grew from melt while the pressure of the impact that launched the rock was still high.
How it is recognised
It is identified with transmission electron microscopy, diffraction and microprobe analysis.
Did you know?
Don Wilhelms wrote a well-known history of the geological study of the Moon during the Apollo era.
Its crystals grew in just seconds, while the shock wave of an impact passed through the rock.