Historically, gem materials of a biological origin were called organic. The term organic can be confusing as a definition by itself because of its use as a clarifying word for natural substance that has had no additional chemical intervention.
This is a big topic and I may split it into a couple of blogs. There are so many facets to sustainability. Sustainability is acting to avoid the depletion of natural resources in order to maintain an ecological balance. Oysters are naturally a great source to maintain the marine biodiversity because they are filter feeders.