Unremovable white powdery residue after wet sanding wood

I’m new to woodworking and know very little, so apologies if this is an extremely basic question or I’m doing something completely wrong. Recently I’ve tried to sand away a few imperfections on a Snakewood pen blank I bought, using 220 grit sandpaper initially and following up with 600 grit. So far so good and I was able to remove the imperfections.

However then when my wood dried there was a chalky white residue on it. I’ve attached pictures to demonstrate, the blank on the right is the sanded one and on the left I have another snakewood pen blank which the sanded one looked like initially. I’m not sure what initial finish was applied to the blank on the left.

I’m not sure what this residue is but I would guess it is a mixed slurry of silicon carbide from the sandpaper and the wood the sanding shaved off. This is aesthetically quite displeasing so I tried getting rid of it. When I wet the blank it looks normal again but the white residue reappears as it dries, so I guess it is stuck in the grain of the wood.

So far I’ve looked up this issue on the internet and the recommendations range from washing down with a microfibre cloth (no effect), sanding further with different grits (no effect) to oiling the wood with mineral oil (again it looks OK when oiled but the white residue reappears as the oil gets absorbed) to using turpentine to get rid of the residue (again no effect, it reappears when the blank dries).

I’ve also had this issue before when sanding wood, especially when I’m only sanding part of the piece: when wet everything looks good but upon drying a white residue forms over the sanded area that is near impossible to remove.

Does anyone know concretely what this residue is and what is the best way to get rid of it? Thanks in advance for all your help!

(click to enlarge images)