Moissanite
Silicon carbide; its microscopic grains in chondrites are stardust older than the Sun.
Key facts
- Formula
- SiC
- Family
- Phosphides, carbides, nitrides and silicides
- Crystal system
- Hexagonal (also cubic forms)
- First described
- the Canyon Diablo iron meteorite, 1905
Moissanite was named in 1905 after the French chemist Henri Moissan, who reported silicon carbide in the Canyon Diablo iron meteorite in 1904. His sample may have been contaminated with the artificial abrasive carborundum, but natural moissanite has since been confirmed, including as presolar grains in meteorites.
What it is
Moissanite is silicon carbide, almost as hard as diamond. It forms where carbon is more abundant than oxygen, conditions found in the outflows of certain stars.
Where it is found
Microscopic silicon carbide grains have been extracted from primitive chondrites such as Murchison by dissolving the rest of the meteorite in acid. Their isotopes of carbon, nitrogen, silicon and trapped noble gases are completely unlike Solar System values. Most formed in the winds of carbon-rich red giant stars, and some in exploding stars, before the Sun was born. Some are about 7 billion years old.
How it is recognised
Presolar grains are typically a micrometre across and are found by their isotopes with an ion microprobe. Artificial moissanite is sold as a diamond substitute.
Did you know?
Each presolar silicon carbide grain carries the isotopes of a single star, so scientists can study stars by analysing grains in a laboratory.
The first presolar silicon carbide grains were identified in the late 1980s.