Glass

Glass is an almost completely transparent block which is very useful for windows and transparent floors/ceilings. It was added in version 0.0.19a. It is not affected by gravity, it is solid and allows light to pass through it. Glass is availble in Creative mode. In Survival, glass is not available for use. However, in Indev and Infdev, smelting a block of sand will create a block of glass. When broken, the block cannot be gathered again. This means that glass is limited and should be used wisely.