I don't think your floors are slate. Slate is a natural stone and is the same color all the way through. Lots of older homes around here have slate floors and roofs and none of them flake and have white in them.

That is slate and when it flakes, the underlying levels are not necessarily the same color as the uppermost layer. It’s not a quality issue, is nature of the stone. Fifteen years of harsh cleaners, infrequent sealing and temp variations will cause the flaking. Good that you sealed, and adequate strategy to paint the exposed areas if you’re planning to move in 1 year. You could also replace the flaky ones but 1) you’ll soon realize you need to replace a bunch and 2) the new tiles will stand out quite a bit.

your biggest concern while you live with it is to use a cleaner for natural stone (or just water) and to walk cautiously as the flaked areas, if big enough, can be tripping hazards.

bossyvossy. In SW PA our slate is variations of the same color through the whole slab. Usually grays to blacks. I would love to have a slate roof on my house, but it is $$$$. Wonder where this slate comes from?

This is slate

And this is also slate, shown in different colors, in 4 tile settings. Mined from all kinds of places around the globe.

I think what you're seeing as a white color where the tile has flaked is actually inaccurate due to the photo. it looks like it might have some color tint to it that you're not seeing due to lighting, and of course, it would be much lighter being it's unsealed.

That said, flaking (what's actually called "shaling") is a normal thing with slate, and especially natural cleft slate. Just the way it is, and one of the reasons I recommend against using any kind of top coat sealer on it. But being this has already been sealed, my suggestion would be to just touch the newly shown raw areas with sealer to match the rest of the floor

You can use acrylic paint from the craft shop and then seal but if your guy sealed entire floor, including flaked areas, it won’t take that paint for many years to come. (That means sealer is doing its job)

maybe it depends on geographical area but where I live, slate flaking or shaling would double w/o sealer. But I will admit this is a controversial subject. I didn’t seal my marble and some people think it’s madness not to seal. Add to it the fact that many sealer manufacturers claim 10 year durability when actual stone looks like it needs reseal in 2-3 years, and I am not at all convinced that we know everything there is to know about sealers: Which is best, durability, etc.

Thanks everyone! The colors that exposed is a lighter gray/red. I don't know much about natural stone, but due to the "shaling" I can tell it is not ceramic. Also a sheet literally comes off, it is not just worn down. It peels off. Should we sand the sides where the shaling has happened? We did not last time and now a tiny hole is a big hole. Any way to stop this section from continuing to deteriorate? Even with the sealant? The rest of the floor is in really good shape, it is just this section which is really high traffic. Any suggestions would be greatly appreciated. Thanks!

Seal the exposed areas after a bit of sanding to ease the sharp exposed edges. I have 50 year old slate in my house and it does quit that eventually.

This is definitely a slate material. It looks a lot like what we used to call "KUND" slate which comes from India. It's actually attractive for specific applications yet this shalling issue, from my experience, is common in time. I've used different sealants only to find that most fail and peal in time. What I do with my personal floor is stain the specific areas that shale and then once dry I apply another coat of sealant. ~~ My best advice as a mason of 38 years is to just not use this product for horizontal surfaces ( since "feet" , etc. seem to help in peeling the shaling stone) and definitely don't use this specific slate outdoors especially if you want a gloss sealant.