Serpentine is a rock forming mineral found in many metamorphic and igneous rocks with chemical formula (Mg,Fe)3Si2O5(OH)4 and chemical name Magnesium Iron Silicate Hydroxide. The colour is mostly green and the crystals are translucent. In my Sand Atlas collection I have one sand with serpentine (no. 278) originating from Marine d’Albo on Corsica island in France (Ligurian Sea).