Strtspdlx,
Re :-
In your first post the first picture I strongly think the crud you have is fine turned off metal particles and shavings that have entered the bearing cavity via the clearance gap of the thin sheet metal caps that cover either side of the the bearings.
When I took possession off my lathe in August last year the lathe was noisy and" heavy " running off load . I found the bearing grease ( Yes , I have grease caps/points as original fittings ) bleed out had brass , aluminium and what looked like cast iron particles in it after I washed it out in a carbon tetrachloride ( CTC) de-greaser to see what the metal content was .
On taking head stock shaft out (mine is held in by removable bearing caps ) there was loads of metal & grease crud identical to what you show that flushed out the taper bearings when I washed them out with CTC and a 1/2 " paint brush . Once cleaned & dried off I re greased them , reassembled everything then refilled the grease pots .... the lathe now runs as quite as a mouse and as smooth as silk at the headstock .
My next step is to alleviate a noisy cross shaft that flings out the daily oil lubrication like there is no tomorrow , it has evidently been run dry for a long time as the cross shaft ends in the bearings bears 2 battle wounds " .
I hope to make new bearing blocks and insert a pair of circlip retained sealed for life high speed ball bearing races in each mounting block instead of messing around with phosphor bronze to make precision reamed bearings & all that that entails .