Glass is comprised mainly of sand (silica). Since iron is in sand, this causes the glass to sometimes have greenish tones and hues. Iron is a component used in bottle-glass.
Glass is a combination of sand, flint, spar, as well as some other siliceous substances, with a fixed alkali. if an alkali is used to create glass, soda is often a prevalent choice.Another possible glass-creation component is metallic oxide. White sand is the most sought after--it requires no preparation for coarse goods, as it is almost pure. A simple wash of the sand in water will produce glass of higher quality. Thus, the whiter the sand, the clearer and purer the glass!
Another alternative for a metallic oxide component is litharge (a preparation of lead).
How Glass is Made
In order to produce glass from sand, the furnace/heating mechanism must reach the temperature of approximately 3,600°F, or 1,982°C. It cannot be produced in your oven, that' s for sure!
Natural Glass
Obsidian is a natural glass that is found near volcanoes.
Moldavite is also another form of natural glass, a creation in the sea.