I've noticed that every time I change the oil in a mower it has some fine glittery stuff in it. Mowers seem to last a long time, though.
Mine don't look like that? Black if it went along time before a change.
I bought my mower "well taken care of" used - -
I change the oil about every 5 years now that the shavings & grit has been flushed out the first few times the oil was changed. The oil still looks great. I might maybe change it this year.