The hesalite has a bit of a domed shape, the sapphire flat. The hesalite has more of a warm glow. The idea of polishing the crystal is at first intimidating but it is no more of a job than shining a pair of shoes. NASA choose hesalite because it doesn't shatter like the sapphire crystal. This would be a disaster in space with no gravity.
Here is an early morning photo of the speedy w/hesalite crystal
