Glass

Glass is a block that first appeared in Creative version 0.0.18a_02. It has an almost completely transparent texture put on all six sides of the block. Glass is not a natural block, and is never generated as part of the terrain. Glass blocks adjacent to other glass blocks are invisible when viewed through glass. Sunlight can penetrate through glass, making glass useful for buildings such as greenhouses. Although glass breaks very quickly with no tool, swords can be used to hasten the process slightly with a penalty of one extra use per block destroyed.

Glass will not hinder a redstone current from travel down the side of a block diagonal to it.

Be careful where you place Glass as when it is destroyed, it will shatter and give nothing.

Torches, Redstone (Wire), Jack-O-Lanterns, Minecart Tracks, Doors, Pressure Plates, Beds and Ladders can not be placed on glass.

Glass blocks are crafted by smelting a block of sand.

Trivia

 * In Survival Test mode, glass blocks could be broken very quickly and would drop a glass block to pick up. The only way to obtain glass blocks at that time was to place them on the map before the level was loaded in the client.
 * Notch has expressed low-priority desire to implement tile-to-tile support so when Sand comes into contact with Lava, it creates Glass.
 * When water is above glass, an infinite source cannot be created.
 * When attempting to light glass on fire with the Flint and Steel, the durability of the tool is lowered without any flames appearing.
 * Arrows will not break Glass when fired at it.
 * Placing a glass block on top of a chest does not prevent the chest from being opened.
 * Clouds seen through the glass disappear while the glass is being broken.
 * Glass towers ( 1x1x3-5) can create light underwater via sunlight
 * Glass placed next to water running downwards will make the water run more quickly and violently; this can be useful in making traps.
 * When Glass is placed over a dropped item, the item is trapped inside the glass. You can also drop items into Glass.
 * Glass used to have a different texture when it was first created. Old Glass.png
 * Glass can be used for placing Redstone, ladders, torches or saplings on top on blocks that they can't normally be placed on like chests and furnaces by placing glass one block higher beside the chest/furnace and trying to place the Redstone, ladder, torches etc. on the side of the glass. This will place it onto the chest/furnace.
 * Rain used to fall through glass, even if you were under a solid block. This was fixed in 1.5_01

Glas Szkło