> Maybe I'm ahead of myself. Let me explain, I haven't even FOUND the sandstone caverns. I've gotten through both the railway barriers, and I've found some pillar that I can't knock down and a little pond to splash in. I think if i find the caverns, i can advance in the game. I also haven't figured out what the HEEC is for. Thanks for everyone's help, though. Here's my inventory again:
>
> 2 Nanoxite Stones
> Scrap of Paper
> Silver Key
> Pickaxe
> Washcloth
>
> 5 Peryolitium Shards
> I.D. Card
> Gold Key
> Wrench
> Round Pot
>
> Leather Briefcase
> Passcard (CQ20024)
> Peryolitium Key
> Noise Filter Headset
> Small Mirror
>
> Employment Papers
> Passcard (CQ30021)
> Vault Key
> Knife
> Sleeping Pills
>
> ISO Access Form
> Passcard (CQ60537)
> Dragon Key
> ISO Energy Pulse Gun
> Rock
>
> Violations Report
> Supply Room Card
> Crowbar
> Tranquilizer Gun
> Tranquilizer Spray
>
> Experimental Results Papers
> Mine Access Card
> Light Tube
> Military Uniform
>
> Beetle Analysis Papers
> OSA Card
> Radio Receiver
> ISO Officer's Cap
>
> Peryolitium Shell Diagrams
> Izacladia Access Card
> Fire Extinguisher
> Pet Snacks
>
> ISO Accident Report
> Business Card
> Crank
> Matches
>
>

You really need to try and get into the sandstone caverns, it's really a matter of exploring as deep as you can and then some more!And dig!!
There's someone you should meet if you go deep enough.

Take note of the info that comes up as you explore, especially if you come off of a cart, but above all else MAKE A MAP, especially of the sandstone area, if you don't you'll go insane!!

Try one of the guys on the business card, he may be interested in a trade.
Hope that helps :o)