That's not looking too good. While waiting on the builder, you might search the Houzz archives to see if anyone else has encountered the problem, but with this being a new build, I wouldn't touch it any further at all so they don't blame the damage on you.

Try some acetone on a soft white rag please. Don't be afraid to rub a bit; it may be smeared silicone.

Thank you! I’m definitely going to wait to hear back from the builder, but I will give the acetone a try as well. Is silicone what they use to install the countertop and does this happen often? Does it have to be a certain kind of acetone and will it harm the surface?

yes, I was thinking that somebody with some kind of glue on their hands touched it. I've literally just used nail polish remover on things like that (the acetone is more diluted). you might even be able to use a magic eraser.

BUT you might want to contact the manufacturer of the quartz first and get a list of dos and don'ts for cleaning your specific type of quartz. and just to be extra careful, do a spot test on a sample scrap.

Hi Adrienne were you able to solve/remove the streaks in your quartz? We had our quartz countertops installed 5 days ago and basically haven't used the island countertop because the island sink has no faucet yet. Basically, we are having the exact same issue.

I'm curious if the installers and/or quartz company was able to solve this or was it/is it a battle to get the quartz redone. Sorry i don't know how to private message on here if that's even possible.

@B K I dont' know if you'll get a response from the original poster or not, but the general advice here at Houzz for situations like this is to document everything by traceable methods like texts or emails and get the responsible parties back on site as soon as possible to negotiate a solution. If you have not yet paid in full, withhold your final payment. You may need to end up filing in small claims court or getting a laywer to assist if your cost was roughly at $5,000 USD or higher and the installer is unable or unwilling to fix the problem. I'm so sorry you're dealing with this issue. You might want to consider going back with Cambria or a higher quality of quartz to avoid future issues like this if it is more than just surface glue as alluded to above. I would really hesitate to do any type of cleaning before the responsible party has a look at it just so that you are not furthering any possible damage to the surface.

The acetone bath I recommended earlier will not harm the estone, however, it may remove the streaks.

Many estone manufacturers including Cambria recommend against using acetone on their products, so while it may be true that acetone won't harm quartz with a short exposure, you could void your warranty by using it. Since the product was recently installed and is still under warranty, waiting for the responsible party to negotiate a fix would be the safer route.

I have been using acetone on estone since the inception of the industry over 20 years ago with no damage ever.

No doubt, @Joseph Corlett, LLC, that you've had success. Acetone just isn't on the list of approved cleaners for a warranty claim for most estone, Cambria included: https://cambriausa.widen.net/s/dfv5woy4sp

Silverlined:

Corian seams would still be made with silicone instead of methacrylate were it up to DuPont, Corian's manufacturer, nor would there be any thermoforming. People would foolishly believe they couldn't undermount a 33" sink into a 33" cabinet if they followed the sink manufacturer's instructions. Plus they would use the leaking and difficult-to-install sink clips provided by the manufacturer.

What's gong on here? Manufacturers aren't innovators. Guys who have to sell, fabricate, install, and resolve the callbacks of the manufacturer's products are.

You can set a hot cookie sheet directly on Corian without harm and in defiance of DuPont's instructions. You cannot do the same with a red hot cast iron pan. Manufacturer's cannot specify nuance, so they ban everything because people are generally idiots. That's why acetone doesn't make the list. No you can't let it dwell trapped under a can, however, a quick swipe on a clean rag will never do any harm.

You can believe the manufacturer who has already been paid or you can believe the guy who isn't going to get a check unless he successfully and quickly resolves the callback.

My previous comments stand. This was a warranty issue with concomitant advice to let those responsible address the matter. I'm glad to hear the issue was resolved by the responsible party. I agree as @Joseph Corlett, LLC has stated here and elsewhere that acetone is indeed capable of damaging quartz given enough contact time:
https://www.houzz.com/discussions/4327458/how-to-get-paint-thinner-out-of-quartz
True, manufacturers' guidelines about such substances are naturally issued out of an abundance of caution. The rules of the fix-it game obviously change as to what a homeowner might want try DIY for a countertop once warranty is no longer a factor.

Hello Nice that you got it professionally fix. I myself am a quartz technician but I’ve been having issues with that same countertop in constructions homes today. if possible can you provide me with the company that installed this countertop I would love to reach out to them for a tips on what products they used.

the op said they didn't use a product. the countertop had to be buffed to get the streaks out.

yea i know but i’m wondering what buffing compound was used.

Jose G:

You're looking for Quartz Renew from Regent Stone Products.

Joseph:

Tried that before but it didn’t work.