Well let me tell you. Glass is a mixture of silica, soda and lime fused together at extremely high temperatures. This is known as soda -glass.
When lead-oxide is added to the mixture in excess of 20% it is known as lead glass or crystal. This type of glass is very bright and clear and looks awesome when cut into.
Add boric-oxide to the mix you will have on your hands a very durable and strong glass. Did you know pyrex bowls are made of this type of glass?
Fiber-glass is nothing but regular soda glass made into long thin strands of glass and then cut to size. This makes a very good insulation.
By adding different chemicals, at different temperatures you can get the whole cornucopia of colors. Add different metals and gems, you increase the color variances. For example: shades of brown can be made by adding iron-sulphide to the mix. Green and be achieved by adding iron-chromite and blue can be achieved by adding cobalt.
Glass can also be found in nature near a volcano or where a meteorite has hit the earth. Obsidian is the geological name for glass. It is formed when the sand that is shot up from the volcano mixes with lava and melts into a shiny dark green or black hard material. Obsidian has been used by man from the ancient times as hunting tools. Maldavite glass is a well known green colored glass where earth was hit by a meteorite.