you spelled it right and I didn't. Silicon is widely used, but I don't know if it is always in silcate form. You have to wonder if someone noticed the type of sand they were casting pistons in and decided to dump some in or if it was an accident to begin with.
Who knows.... I'm sure there are people way smarter than us that were doing R&D somewhere for someone designing faster and better pistons that recognized the heat transfer and natural lubricities offered by silicates or silicones or vagina sand...