Cultured marble. Not actually marble but made to look like it.

Thank you, any suggestions to get ring in it out? I think it is from hard water

Pack a towel soaked in white vinegar on it for a few hours. Check periodically to see if it’s working.

Thank you all for the suggestions & comments

Possibly corian. it looks similar to ours, and our house was built in 1974. perhaps use a flashlightr, open the cabinet, and see if you can find writing or clues on the underside.

https://www.corian.com

we were able to use fine grit sand paper to get rid of stains.

Crazing around the drain with cultured marble is impossible to get rid of. It signals that it is time for a replacement.

The dirt and grime went into the unpolished cut area for the drain over time and there is no way to get it out. .......You might remove the drain plug then stuff something inside the drain to clog it temperoarily being sure you do not plug the drain permantelyand then pour bleach in it in hopes it will soak into the stain area. This is a risky procedure. However, you will be wasting your time because it will stain again. I personally would replace the countertop/sink.

Try CLR for hard water stains maybe🤷🏼‍♀️

It's not Corian or any other solid surface; it's cultured marble. I'm not optimistic about stain removal. Replacement please.

Thanks all! I have tried multiple cleaners and it does not come out- will replace.