Allergy test
Take a sharp object, such as a key, and scratch it hard on the table, which proves that it is real quartz stone, not granite, not acrylic.
Acid liquid test
Drop lemon or acidic liquid on the board to see if it will leave traces. If it will, it will prove that there are many things containing calcium, which is unqualified.
Impurity detection
See if there are many impurities on the board, such as your white quartz stone. There are many small black spots or yellow spots on the board, which proves that the quartz sand has not been screened.