I thought I would post about this today to save a lot of confusion. Many people ask me if these are truffles. A common and easy mistake to make for the novice forager although quite difficult explaining to people when they think they have hit a gold mine that these are in fact Earthballs or False Truffles, hate being a kill joy! However glad I got there before they decided to eat it. Earthballs smell quite pleasant and mushroomy its understandable some might be tempted but visually its a mass of black unpleasant looking spores, not remotely appealing to eat. Most Earthballs are poisonous too or certainly not edible. There are other species within this genus that look similar to the Common Earthball, the Leopard Earthball and the Scaly Earthball.
The pictures below sent in (thank you Richard/Arthur Dailey ;-)) I believe of an immature Scleroderma spp, sometimes hard to id 100% by photo, non the less not truffle! Microscopic examination of the spores from a mature specimen is sometimes necessary to determine correct species with this genus. When spores are mature they turn black.
Again these photos below are not truffle,(thank you Thomas Mcclymont)I believe to be mature Yellow False Truffles, Rhizopogon genus they have initially a thick, smooth outer wall covered in mycelium strands which can become cracked with age as do most Scleroderma species. A good example of the black tar like spores, this is what to expect when looking at the inside of either of these mature species, otherwise they are whitish/cream coloured when young as above.
This is what the inside of a truffle T aestivum should look like, marbled brown and with light veins running throughout the fruiting body.
Or when young and immature like in my logo picture, the gleba are white inside.
The outside of the Summer truffle should have black premedical warts like pictured below.
Hope this helps!