The Glass Fusion
Glass is obtained by fusion in a very high temperature furnace of an homogenous mixture of minerals (vitrifiable mixture), called primary materials, which are mixed in appropriate proportions in weight, and glass scraps.
Types of Glass
Glass also exists in a natural state. The most common one is obsidian, a dark shiny material, which is very hard, formed in volcanic rocks and which man learnt to produce to make objects (blades, arrow-heads, etc.) over one million years ago.