That would be a mix of peat, just plain dirt, a little vermiculite and some fine sand. Now this particular beding is almost a year old as the peat has broken down, I stir the mix regularly with water and screen it for urates and such, it seems to have become more packable and holds a burrow well. Now in the top dead middle of that mound there is one round support underneath just to keep the deepest part of the chamber from clapsing. But it did take time I was watering every other day to keep it hoding together but as I have screened the large peat chunks out and as the rest broke down with good regular stirring it has become very soft and very fine. Works for me I think it would work well for a black throat but I know most use just plain dirt deep and well packed.
Anyway thanks for looking 