My grandfather was a volcanologist and had a large collection of rare minerals and stones, some of which I inherited. Looking through our storage unit today I noticed a bag of black what I thought were rocks. I have since realized that they are pieces of black Hawai'ian coral (we are from Hawai'i). He passed away in the 90s so they are at least that old. He used to make jewelry as a hobby so I assume that is why he had them. My question - is black coral valuable and considered a "treasure find"? From what I understand it is rare now. Thanks!