[Don't throw] pearls before swine. Based on the verse found in the Bible; Matthew 7:6 in which it is written: "Give not that which is holy unto the dogs, neither cast ye your pearls before swine, lest they trample them under their feet, and turn again and rend you" [tear you into pieces].
A caution against offering the uncultured anything of quality; or, a caution against presenting anything to those who have no appreciation for the value of the product that has been created.
One ancient use of margaritomancy involved throwing a pearl into a cast iron pot sitting in a fire and watching it to determine a person's guilt or innocence in a crime. If the pearl started to move, then the person was believed to be guilty. If it stayed in place, then he or she was not guilty.