Tutorials/Cobblestone farming

Cobblestone farming uses a Cobblestone generator to produce cobblestone without damaging the terrain. Cobblestone generators work on the principle that when a lava stream comes into contact with water, the lava is turned into cobblestone. This fresh cobblestone then prevents the two streams from touching. When this fresh cobblestone is removed, the two fluids will produce another piece of cobblestone.

Many generator designs exist, but the most basic is a 10-block long trench with a water source block at one end, and a lava source block at the other. This will create cobblestone next to the lava source block.

One must be careful not to accidently create obsidian, which happens when water comes into contact with a lava source block (See Tutorials/Obsidian Farming). A basic understanding of fluids is helpful to prevent this.

Standard Cobblestone Generator
Standard generators have been around for quite a while. Their popularity, however, is limited because cobblestone is so readily available. Standard generators have the player mine the fresh cobblestone, which they then collect. The main issue with this type of cobblestone generator is that the item can fall into the lava, destroying the item. Even though cobblestone is a renewable resource, this greatly reduces efficiency.

Two sample designs: It is suggested to use obsidian blocks behind the lava source blocks, as this will stop you from accidentally mining a hole in the back wall.
 * Fountain Style

This design features a lower chance of the cobblestone being destroyed by lava, but it is significantly larger.
 * From Below

Piston Cobblestone Generator
Pistons can be used to automate the cobblestone generator. Piston cobblestone generators, work on the same principle as standard generators, but, rather than mining, a piston is what clears the fresh cobblestone allowing the streams to touch once again. Piston cobblestone generators can be used in two ways, to create a large supply of cobblestone that the player can mine later, or to keep the cobblestone as blocks, which can be used for self-repairing structures.

Components
There are three basic components to consider in a piston cobblestone generator:
 * The Core. This part includes the water and lava that creates the fresh cobblestone.
 * A clock generator. This part sends a pulse to the piston that pushes fresh cobblestone out.
 * Secondary Pistons. These parts move the fresh cobblestone further, allowing for more cobblestone to be generated.

The Core
This part can be very similar to standard cobblestone generators. The lava and water mix in front of the piston. One thing to consider is that the piston must be accessible by redstone. There is a hole at the end of the water stream which draws the water straight. When attached to a redstone clock, this will create a single row of cobblestone 13 blocks long (since the limit a piston can push blocks is 12 blocks).

Redstone Clock Generator
A basic understanding of redstone is helpful but not necessarily required. The ideal clock will send a pulse shortly after the cobblestone has been created, making way for a new piece of cobblestone. But since lava spreads so slowly, this can be difficult to achieve.

I suggest either a piston clock or a 4 sided repeater clock because both have four outputs. Attach one of the outputs to your core. If each quarter of the clock has the same delay, the piston will be retracted for 3/4 of the cycle. This allows the lava more time to spread to the open space in front of the piston.

Secondary Pistons
Since pistons can only push a maximum of 12 blocks, the core will only produce a limit of 13 cobblestone blocks. This can be greatly increased with secondary pistons that guide the row of cobblestone in other directions. In a way, it is a similar idea as the core piston in that it removes the fresh cobblestone in order for more to be created. Self repairing structures tend to use several secondary pistosns and one or two cores.

Triggering a secondary piston can be done a few ways. The secondary pistons can be connected to the same redstone clock as the core, which frequently extends an empty piston. This can be annoying if you are working in the area. Alternatively, a Redstone Repeater can send a signal through the block which detects when a peice of cobblestone is present. This can then send a signal to a line of secondary pistons which trigger simultaneously.

Video Tutorials/Examples
This uses a four sided repeater clock, but with uneven delay. The piston is retracted for 5/6th of the cycle
 * Piston generator

This shows how signals can go through blocks using repeaters and lowered redstone torches.
 * Block Detector

This shows how secondary pistons move the row of cobblestone from the core.
 * Secondary Pistons