Anonymous,
I am not sure if the following falls under "spirituality" or somewhere else - but for me it is neither fisical nor mental.

I'd call it a spark. There are people who seem to have very good technique, train a lot, are capable of holding the pressures of competitions or even hostile judges. Yet there is no passion or spark in their dance. Sometime it looks like they are perfect - but do not live what they dance. They do not show the emotional side - just the mechanical precision.

Perhaps part of this is due to technique, to the fact they do not train their facial expression that much - but I'd still place that in a sperate category. The spark, the passion, giving themsleves to the music...