Types of Presolar Material
Presolar grains consisting of the following minerals have so far been identified:
- diamond (C) nanometer-sized grains (~ 2.6 nm diameter) possibly formed by vapor deposition
- graphite (C) particles and onions, some with unlayered graphene cores
- silicon carbide (SiC) submicrometer to micrometer sized grains. Presolar SiC occurs as single-polytype grains or polytype intergrowths. The atomic structures observed contain the two lowest order polytypes: hexagonal 2H and cubic 3C (with varying degrees of stacking fault disorder) as well as 1-dimensionally disordered SiC grains. In comparison, terrestrial laboratory synthesized SiC is known to form over a hundred different polytypes.
- titanium carbide (TiC) and other carbides within C and SiC grains
- silicon nitride (Si3N4)
- corundum (Al2O3)
- spinel (MgAl2O4)
- hibonite ((Ca,Ce)(Al,Ti,Mg)12O19)
- titanium oxide (TiO2)
- silicate minerals (olivine and pyroxene)
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