My first instinct is to say- can you get a refund?! My sister bought real black slate tiles for her newly built barn conversion 3 or 4 years ago, they had to be sealed and this has to be done very carefully as any imperfection in the seal can be easily seen. After that they have to be sealed again every few years I think. In any case she found them a nightmare- she was ( no exaggeration) cleaning them every single day as they showed up every bit of dust and dirt, and just walking in and out of the house made them dirty. Last year she got so tired of it, she had them all taken up and replaced! Same thing with friends of ours, they got black slate tiles in their newly built house, but then sold and when they built again, they vowed never again a black floor. We were well warned and went for a completely different colour, but when we were installing a stone fireplace in a room with a wooden floor, we needed a tile surround between the fireplace and the wood and in a hurry chose a black tile- its just a small area so its not too bad, but I can see dust on it all the time- I wouldn't like to see it in a large area!