This is a giant single crystal of garnet from a place called Dora Maira, Italy. It is special for several reasons. One is the unusual size of garnet crystals. Two is the unusual pale pink almost white color of the garnet, which reflects its almost pure Mg (as opposed to Fe, Ca, Mn) content. And, finally, this rock was subducted to extreme depths and pressures in the earth... it came from at least 100 km depth... and through a freak tectonic accident was dragged back to the surface in the Alps.