Unusual substance in cam cover

Hi, today I went to clean my cam covers to put them on my engine and I noticed an unusual substance in the front cam cover (the black one). It is a clear, hard, substance, almost like finely crushed glass. I am really confused as to what it is, and how it got there. It is in an inaccessible area too, so I’m not sure to how to clean it. I really don’t want this to get in my oil, as I am in the process of rebuilding my engine after some spun bearings. I have attached some pictures. The close up is in the area shown in the red circle.

Looks a bit like aluminium oxide crystals- the cam covers are aluminium so if they are exposed slowly over time to moisture you can form large crystals of Al2O3.

That makes sense, as the previous owner reported seeing water when he opened the sump. This car has a weird history.