For every piece of crystal armour worn excluding the first piece, the maximum amount of crystals dropped increases by 1. For example, using 3 parts will cause them to drop 2–5 crystals.
Without wearing any crystal armour pieces, getting 2 crystals is more common than getting 3 crystals.
Without wearing any crystal armour pieces, 1-2 crystals are dropped with the main drop and 1 shortly afterwards. The first drop can be boosted with crystal armour.