Asphalt shingles are coated with a thin layer of mineral granules. Over time these erode. Slate and other solid shingles such as tiles have no granule mineral layer so there's nothing to erode away.

Thanks, my insurance company had a review company come look at my house and reported that slate roof had granular loss.

Slate shingles can flake, but the flakes do not look like granules. I'd ask my ins. co about that review companies expertise.

Lol @lazy_gardens! Agree that they can flake.

Real slate shingles, I guess the person doing the review is incompetent.

I would be challenging the reviewer's assessment. Talk to someone at your insurance company.

I did talk to the insurance agent we have but their reply was more or less oh well. I posted a comment on the "good hands" insurance main FB page and the head office is looking into what is now a fiasco. Our original policy was canceled due to a claim after 20 years with the company, so our insurance agent made another policy. Now, this review of the roof has made the new policy be canceled. Found out from other insurance agents that the original policy could have been kept with an exclusion (animal, now passed on, had nipped someone on the finger) added to it. Sorry for the story, just tired of the drama from the insurance company.