Me and my friend were playing mine craft survival and we noticed that a strange unbreakable block appeared under our carpet. It looks just like a normal block with four egg like shapes around it and a silver almost circle in the middle. Inside the circle there are 5 small squares, the middle one is dark purple and the others are pink, red, green and light yellow. What is it?
The block you are describing is definitely a command block. See CannonFoddr's attatchment. Are you and your friend the only ones on the server? The only way to get a command block while in survival mode is to cheat it in. I would ask your friend to do some explaining.