Are Silk milk half gallon cartons made of recyclable plastic?

If they are made of plastic, there is no number indicating what type of plastic. If they are not made of plastic, then what material? I would like to recycle them, but I cannot figure this out. The website states "Silk soymilk cartons can be recycled after removing the plastic screw cap", but this doesn't tell me if the carton is plastic.|||They are Tetra Pak, which is recyclable, but only in certain areas. You'll need to do an internet search for facilities near you which can recycle the packaging.