Borosilicate glass is often called "Hard Glass," mainly consists of silica and boron oxide. Borosilicate glass is known for being less dense than ordinary glass (soda-lime glass, often called "Soft Glass") and has a very low thermal expansion coefficient, about one-third that of ordinary glass. This reduces material stresses caused by temperature gradients, thus making it more resistant to breaking and with its superior durability, chemical and heat resistance this glass finds excellent use in chemical laboratory equipment, telescope mirrors (The Hubble Space Telescope), where it is essential to have very little deviation in shape.
This video was made solely with the intention of showing the durability of our glass pendants & glass jewelry, hence the “GLASS” they can and will break. They are like diamonds – they will withstand the test of time, but not a hammer. Do not try this at home.
Did you know the Space Shuttle's black Insulation Tiles has a coating of Hard Glass on them??