Granite, no way is it marble, as in ive never seen a marble that looks that terrible…..
Ha. Its a decent low to mid level granite.
The 25 years warranty is due to a specific type of sealer that some places can put on.
IF YOU REALLY WANT TO CHECK take a blade to the underside. If it scratches easily then, well I guess it could be a granite alternative or a high end granite with more mica.