Try dripping a few droplets of water in the same area. If the water beads up (i.e., doesn't absorb into the stone and leave dark/shadowy spots), it's likely the ring is an oil stain -- which means your contractor likely didn't use a sealer that protects against both water- and oil-based liquids. Any idea what brand he used? Also, what type quartzite do you have? Close-up looks similar to my Calacatta Gold.

Are you saying it is one slab and you just installed the window over it? That doesn't seem like a great idea. I would have preferred to have the window installed first and made sure it was self contained and weather proof. Then you would install the counters as two separate pieces. No one would know that it was or wasn't one slab. Your quartzite is probably porous so you might have moisture wicking from the outside to the inside through the porous slab that you placed under your window. You wouldn't have stained counters if the window had gone in first. Did you test your quartzite? A lot of these "white" quartzites are mislabeled and have many marble properties. I'm not pro, just a homeowners who spent 10 years remodeling a house and the last 3 years designing and building a house and acting as my own designer.

Everyday more and more black spots appearing everywhere.. called the distributor of the stone everyday and his office told me they have received a slab of stone before that was sitting in the warehouse and black spots began appearing on it and they reached out to the quarry but she wasn’t sure of the outcome. This morning i finally got in touch with the owner and am being told that there is nothing that can be done other than him calling the fabricator and seeing if the fabricator can ‘fix the issue.’ He also claims that his office was wrong for telling me that their stones have had black spots appear that never happened. That he’s never seen this before. That the slabs left his warehouse without black spots (which is true, i saw the photos of the original slabs on the flatbed leaving the warehouse)…Not sure what is going on but overall I’m wondering how many more black spots are going to appear… it’s everywhere…….

Search on this forums for "quartzite staining" in Discussions. You will find that this is a common problem with these white/gray quartzites. There is no real fix. Several here have had to replace the counters after unsuccessful attempts to get rid of the stains.