I'm sorry if it's a silly question, but what are those greyish spots behind the stone of this peach (or whatever this is)? What are they for? Are they safe to eat? The fruit is ok from the outside
Callus can develop inside peaches (https://www.tasteofhome.com/article/peach-callus-tissue/), between the mesocarp and the endocarp. Callus is edible and harmless. It's a tissue composed of unorganised parenchyma cells, which in turn are multi-purpose cells that can be found in a number of "soft" tissues with metabolic purposes including, but not limited to, the mesocarp and the endosperm. Callus' main purpose is to seal damaged tissues, see for instance:
- this blogpost that explains the difference between mold and callus in a peach where there actually is a mold infection (which you should not eat)
- its counterpart where there is no mold, but a considerable amount of callus (way more than you have there) was produced because the stone had split open; this one would be safe to eat, once you've ascertained that there is no mold, although callus may contain pieces of hard tissue from the stone.
Small quantities of callus can appear as leftovers form older and smaller lesions.