Earth and sand.
All samples of sand and soil, collected at sea were exposed plates and plastic cups numbered like the order of "picking stations" listed on our "topographic map". Part of the material was used for weighing fixed amounts (1 liter) and obtain the specific weight. For some samples, we extracted the magnetic iron ore: 150 grams per kilogram well. We then separated from the detritus of some minerals bigger sizes more easily recognizable. To determine their specific gravity, we used a bilancetta jeweler. In some cases this value and appearance of the fragments allowed us to recognize the mineral. Many come from the island of Elba, not far from our shores.