The snow and body parts are not consumed by the casting
... but reusing them after the spell's done might be difficult.
By the text of the spell:
The duplicate is a creature, partially real and formed from ice or snow, and it can take actions and otherwise be affected as a normal creature.
We know that the snow and bits are around and animate, at least for the duration of the spell. Plus, when the spell ends, the snow becomes water:
The simulacrum lasts until it drops to 0 hit points, at which point it reverts to snow and melts instantly.
It doesn't explicitly say what happens when it hits the duration, but we can infer it'd be about the same thing as it dropping to 0 hit points.
It also doesn't mention what happens to the hair / fingernail clippings - but they'd probably be left behind in the soupy mess.
Finally, if you cast the spell again, the snow + bits are lost:
If you cast this spell again, any duplicate you created with this spell is instantly destroyed.
Additionally, Spell Components are not consumed unless the spell explicitly says they are which further backs up that the snow and human-parts remain.
The ruby powder, however, is consumed as it is specifically mentioned as being so in the spell description.
Can I use a Foci / Spell component pouch in place of the clippings and snow?
I suppose this depends on the reading of the rule - you're turning a big hunk of snow into a fake person, which is then animated by the force of the spell into a walking thing. If you want to substitute a foci for this...you don't actually have a thing to animate, so I wouldn't allow it.
A strict reading of the rules, though, doesn't cover this particular case - so you possibly could.
Though there's no way you're fitting a full person's worth of snow into a spell component pouch.
