Lava

Lava is a fluid block. It can be found deep underground in caves and at the very bottom of maps. Contact with lava is dangerous and deals damage to players and mobs.

In Classic, lava spreads by duplicating itself to open horizontal and downwards squares like Water. Lava is slower, though, and can be easily outrun. A quick player can block the flow of lava by building a dam. If the lava wave is large, though, a player may not be able to build fast enough. Also like water, lava slows down the player moving through it but it does so to a greater extent. Lava is also more opaque than water and is harder to see through.

If a horizontal lava flow collides with water, Cobblestone is created, but if a vertical lava flow collides with water, the water is removed.. In Alpha v.1.0.6_03 Obsidian is created from water colliding with a lava spring. This "technique" can be used to manipulate water and lava or to harvest cobblestone and obsidian.

Lava's texture was changed in the 0.0.19a client update on June 20, 2009 and is now animated. Lava is luminous and a large lava flow is visible in the dark from quite a distance.

In the survival game mode, lava takes 5 of the player's hitpoints for every second he is exposed to it because it lights him on fire and is extremely hard to put out. It is not possible to drown in lava, as no air bubbles pop up when submerged, but the damage the player takes while swimming inside the lava is often enough to kill the player within a second, even when constantly healing himself. In Indev, if the Hell theme is chosen, most water is replaced with lava.

In Infdev, the amount of damage has been reduced to a half of a heart being removed for every second the player is in lava, in addition to the damage from fire. It will however deal the full 5 hearts of damage if a lava block enters a square the player is in where there wasn't one before, such as placing one where the player is standing or from flowing lava entering the player's block. Lava is no longer present at the bottom of maps in this mode.

You can collect and place Lava blocks using a Bucket. Placing the Lava block will create a Lava spring. When placing the lava spring and scooping it up again, sometimes some of the lava flow doesn't disappear. Reloading the save file may sometimes cause these flows to disappear. As with Water, you can only harvest still Lava blocks (aka springs), not the flowing lava coming from the blocks.

Using a bucket to scoop lava will leave a hole missing from the pool as the lava blocks won't refill the space you took from. With Water, a space adjacent to two Springs will be filled with another spring, but this does not work with lava. The amount of lava blocks in a created world is currently finite and cannot be increased without modding as of Alpha.

Lava can melt ice and snow, much like torches can, but melt a larger area.

As of Seecret Friday Update 9, buckets of lava can be used to fuel a Furnace for 100 smelt; however, the bucket itelf will be consumed in the process. Do not right-click on the furnace while holding your lava bucket, as this will only create a lava spring on top of your furnace!

Trivia

 * Lava is only called lava once it reaches the surface, and is called magma when underground. As such, most of the 'lava' in Minecraft is actually magma.