Instead, test them. That suggests two questions. I'll answer that in the coming minutes.
Testing can present a challenge.
The king of Syracuse had a new crown made. The new crown was supposed to be of pure gold and, indeed, it looked like it was made of pure gold. The king, however, suspected that the goldsmith had mixed in some less expensive silver. So the king asked Archimedes to see if the crown was pure gold or not. Archimedes had a general idea how he would expose the fraud, if, in fact, the goldsmith had worked in some silver.