Your top is probably ruined in that section; proof that engineered stone is not only not "bulletproof", it can't even stand up to normal household detergents with repeated improper exposure.

Hopefully your particular quartz hasn't been discontinued and you can get a piece of color/particulate match. Of course you'll have a seam on each side. If you've got a front sink rail that's fat enough, you can make it the rear and install an apron front sink. I've done that previously. You know you'll get color match then, but with the saw kerf, the seams may be a little wide. These are not:

You may be able to replace the top for the same amount, but you're probably not going to get a spectacular sink like this if you do.

At least your top isn't black estone. This is on a large island; no repairs like yours are possible. It's probably ruined; soap trapped under the red thing.

Any thoughts what causes this though? I'm just a renter and at this point I'm trying to prevent it from getting worse. =(

Apologies for not totally understanding your description on the cause -- are you suggesting that this is caused by likely soap sitting under my sponge tray? I would've never guessed that could cause this =(

I would try a paste of baking soda and water, rub with a microfiber cloth.

I don’t know what a black silicone sponge tray is, but if that’s exactly where a stain appeared I believe I’d throw it away.

Oils from the soap tray if that is a soft silicone leached into the top.

It's a soft tray. It looks like this: https://www.amazon.com/gp/product/B07NLB2XL2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

So it's possible that the tray itself, minus any moisture or heat elements, could have caused this stain? I'm pretty disappointed I wasn't warned about this when purchasing the tray.

Would a stainless steel tray work as well?

Looks like it could be corian.....find out. if it is it's easy to clean.....but corian stains easily.

If it's corian could the stain be removed? And if so, do you have a product/technique that you recommend. Thanks very much!

"....but corian stains easily."

Corian does not stain. Most "stains" are easily wiped away with a green Scotch Brite pad.

After a little more research these do seem like Corian or something similar. Do you all have specific recommendations? I'm a little overwhelmed by the feedback on the internet. I just read an article stating NOT to use scotch brite pads on Corian

HU:

Pull out a drawer please. Look at the bottom of the top. If there is a long black line of block letters with numbers and it says "Corian", you'll know what you have.

If you have Corian or another solid surface, you're in luck because abrading away the spot is easy compared to estone. Your picture of your sink edge looks thicker than 1/2". You may still have Corian, but it may be old 3/4" thickness. I bought my last 3/4" Corian sheets in the mid 90s.

I'm a Certified Corian Fabricator/Installer with over 25 years experience. I refinish solid surface with Scotch Brite pads and other abrasives regularly. If you have a gloss solid surface finish you probably don't want to use a Scotch Brite by hand. No way will the use of a Scotch Brite pad by hand or even under a random orbital sander harm your top if it's solid surface.

Thank you so much, Joseph!

In your last paragraph, are you suggesting that scotch brite pads are *not* to be used on solid surfaces if it's a gloss finish but okay to use on non-glossy solid surfaces? Trying to make sure I'm not misreading. Thank you very much for your expertise!