What materials are used to make a terrarium?

I wouldn't use soil (out of the garden) in a terrarium, unless only plants are to be kept in it. Even then, I would use a compost mixture of a John Innes, type, from a garden centre (UK spelling). If plants and animals are to be kept, use sand or gravel or a mixture of both, after it has been heat or steam sterilized to prevent introducing diseases into the terrarium.