Hearth Glass, also known as hearthstone glass, is a kind of tempered safety glass that can be used to make doors or windows. This type of glass has an incredible density and strength compared to other types of glass which gives it its shatter-resistant nature. It’s because the heat only affects the outermost layer instead on heating throughout all layers like in normal glasses. Even if you break this type of window with immense force, there will still be no shattered pieces but just one big broken piece so nothing bad happens when someone walks past it for example. Tempered Safety Glass is always more expensive than regular glasses due to how much harder they are but they last longer too so it evens out.