The seller made a trade lie.
We asked for asked grinded and solid quartzite stone. Instead of that we got regular river stone.
We got the samples and send them to the laboratory. When we got the results ,we were didn't believe our eyes. There was not single percent of SiO2 (quartz) inside the stones. The mohs hardness was lower than 7 and the toughness was very low.
Fortunately in our case was that we order samples first.