It looks like the change from resistive touchscreen to capacitive touchscreens had resulted in Nokia using Corning's Gorilla Glass, which is advertised as being tougher to break than regular glass as well as being more scratch resistant.
All glass displays on Nokia phones will come from Gorilla Glass according to senior design manager for smartphones, Niilo Alfthan. He tweeted about the displays during a Nokia Design Q&A earlier this morning. Gorilla Glass is infamous because it is very hard to scratch or break, making those screen protectors obsolete.
Nokia had transitioned to glass displays starting with the Nokia X6, which is the first Nokia capacitive touchscreen phone. The Nokia 5800 series phone before that employed a resistive touchscreen layer and did not use glass.