[metalman]

I think that this is far from the first experiment in growing crystals in space, so they must have good evidence for what properties to expect from single crystal silicon grown in space, my guess is that the purity is not so much which elements are or are not included, but more the perfection of the physical crystaline structure, which may introduce the posibility of the crystal having different characteristics in different planes that can be exploited for various purposes.

[georgefrowny]

The crystal planes indeed do have different properties which are exploited already. Some planes have better flatness and defect rates then others, and etching rates and undercutting varies according to the surface orientation and the orientation of long thin details to the bulk lattice.

Silicon boules are grown with defined orientations. There's a system of flat edges ground into the wafers which indicate the orientation.