Oldhamite
Calcium sulphide, which exists only where there was almost no oxygen, as in enstatite meteorites.
Key facts
- Formula
- CaS
- Family
- Sulphides
- Crystal system
- Cubic
- First described
- the Bustee aubrite, 1870
Oldhamite was described in 1870 by the British mineralogist Nevil Story-Maskelyne from the Bustee meteorite, an aubrite that fell in India in 1852. It is named after Thomas Oldham, director of the Geological Survey of India.
What it is
Oldhamite is calcium sulphide. On Earth calcium always combines with oxygen, so oldhamite reacts quickly with moist air and dissolves in water. It survives only in meteorites that formed with very little oxygen. It concentrates the rare earth elements.
Where it is found
It occurs in enstatite chondrites and aubrites, sometimes as large grains in aubrites. It has also been found in some slags and burning coal heaps on Earth.
How it is recognised
It is pale brown to colourless and gives off a faint smell of rotten eggs when it reacts with damp air. In polished section it is grey, isotropic and soft.
Did you know?
Oldhamite in enstatite chondrites holds much of their rare earth elements.
Its sensitivity to water is one reason fresh aubrite falls are so valuable.