When I was in Spain I visited ...

When I was in Spain I visited a Water Treatment Plant using a very fine powder made from finely ground up oyster shells---it is inexpensive and is a waste by-product--after settling it can be used as a soil amendment that provides minerals to the soils along with nutrients from the SS that were precipitated. I am holding a sample but unfortunately they didn't label the sample I have as they consider it proprietary, but I know they get the seashells for free and then have them ground up and packaged in fiber drums. I will ask EAZ in Pamplona what it is (constituents) and post a reply when I have an answer.