terranium

They were built of terranium, a superhard metallic material that had the ability to feed on the earthy crust, making it amenable to growing fauna.

Build a terranium, if you wish. That is, let the boys build it. Don't do the work yourself, for half the interest is in making the thing. Have the boys bring an old berry crate; cut out the slats and take off the top; cover it with fine wire netting […] Put in one or two small plants or shrubs for landscape effect and the terranium is ready. […] Begin on that terranium. […]