which one of the 5 aggregates covers the unconscious mind?

I'd say it would be saṅkhāra (mental formations), saññā is perception which is by definition concious, viññāṇa is conciousness which is by definition concious, but looking at the definition of mental formation it could equally be concious or unconcious.

"mental formations", "impulses", "volition", or "compositional factors" (Skt. samskāra, Pāli saṅkhāra, Tib. 'du-byed) :

all types of mental habits, thoughts, ideas, opinions, prejudices, compulsions, and decisions triggered by an object.

thank you very much bruce. i was tending that way but thought a second opinion might be helpful. if i couldnt find a slot for it, i was faced with SIX aggregates!! LOL

I'd say it would be saṅkhāra (mental formations), saññā is perception which is by definition concious, viññāṇa is conciousness which is by definition concious, but looking at the definition of mental formation it could equally be concious or unconcious.

"mental formations", "impulses", "volition", or "compositional factors" (Skt. samskāra, Pāli saṅkhāra, Tib. 'du-byed) :

all types of mental habits, thoughts, ideas, opinions, prejudices, compulsions, and decisions triggered by an object.