Though the glass is hard but it is fragile under crash. It is great for protecting the display but easily broken with direct crash.
There are several factors to influence the risk of screen break, the glass hardness, the angle of the fall and the hardness of ground. But there is an important thing people always ignore is the the construction between screen glass and phone border. For example, if the screen glass is directly contacting with phone border, the crash can transmit the shock from border to glass even if stress point is not on the screen glass to easily make glass break.
Some phone manufacture has paid attention to this issue and have developed ways to solve it. Phone brand Oneplus did a great job on Oneplus one. They adopt a “V Type” (Suspension technology), which could let screen and border has a V type buffer. When phone drop down, the buffer can reduce the impact that border bring to glass. That is better to protect the screen glass.
Bluboo also noticed the issue and they developed another similar way to solve it. Bluboo adopt a “U Type” buffer between glass and phone border on their 2015 annual flagship Xtouch. They claim the new design could provide higher safety for screen just like Oneplus “V Type” design
Bluboo Xtouch is going to be released on October, 2015. Hope soon we can see it.