I'd second the recommendation of a new Audio technica at-95e if you want a low cost high performance cartridge. It does sound like your cartridge is worn. the black stuff you see on the tip could be vinyl. If you do get an AT95 get and like it get a couple of spare styli now as I think they're being discontinued. When installing the cartridge pay particular attention to overhang and alignment as failure to do so will destroy imaging (as I have learned myself).
Personally I'd chuck the cartridge since LPs are hard to replace, but you could try giving it a little swab with a cotton bud (Q-tip) soaked in isopropyl alcohol. I've always found it to work ok with no negative effects.
Also clean the belt in hot soapy water so it feels sticky and clean the motor shaft and the sub-platter with iso-alcohol so that there's no grease to allow the belt to slip. Finally a little trick I use on my rega is to use double sided tape to hold the felt mat to the glass platter to prevent slippage. Speed stability is not the rega's strongest point but if everything is clean and the mat taped down then it helps a lot.
Personally I'd chuck the cartridge since LPs are hard to replace, but you could try giving it a little swab with a cotton bud (Q-tip) soaked in isopropyl alcohol. I've always found it to work ok with no negative effects.
Also clean the belt in hot soapy water so it feels sticky and clean the motor shaft and the sub-platter with iso-alcohol so that there's no grease to allow the belt to slip. Finally a little trick I use on my rega is to use double sided tape to hold the felt mat to the glass platter to prevent slippage. Speed stability is not the rega's strongest point but if everything is clean and the mat taped down then it helps a lot.