Cobblestone farming is the technique of using 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. Variants of the generator can also produce smooth stone, but this is generally trickier, because for smooth stone, the lava must enter the water from above.
Many generator designs exist, but the most basic is simply a 10-block long trench, with a water and lava source blocks at opposite ends. This will create cobblestone where the fluids meet: Because of their different ranges, this will not be halfway down the trench, but closer to the lava source block.
When producing cobblestone, one must be careful not to let the flowing water touch the lava source block. Doing so will destroy the lava source, converting it into obsidian. A basic understanding of fluids is helpful to prevent this.
While the popularity of building any form of cobblestone generator varies, there are many reasons why a player should build a cobblestone generator.
Here's a list of the most common reasons:
Save the time you'd spend traveling from your shelter to the nearest mine.
Avoid ruining the integrity of a cave or underground shelter.
You're just moving into an area, and want to build without strip-mining the area.
You're building in the middle of the ocean.
You need large amounts of cobblestone, more than you've gotten from mining.
To make a self-repairing object (e.g. wall, floor, pillar).
For particular maps or servers:
Superflat maps tend to be extremely low on resources.
Some Survival Multiplayer Servers tend to have a big demand for cobblestone.
Custom maps or challenge maps sometimes require a cobblestone generator in order to progress (a popular one is Skyblock.)
To get huge amounts of XP by smelting it, using other renewable materials like wood
To make stone or cobblestone related blocks and items renewable (You may want this for stone tools and weapons because they have limited uses.)
Standard (pistonless) cobblestone generator
Standard generators have been around for quite a while. Their popularity, however, is limited because cobblestone is so readily available. Standard generators require the player to mine and collect the fresh cobblestone in proximity to the lava. This both presents risks to the player, and reduces efficiency if the dropped item is destroyed by the lava. These drawbacks may be mitigated by design choices, for example by removing the block under the cobblestone, allowing the loot to fall in a safe place, or collecting drops using a hopper.
Examples of standard cobblestone generators
Notes about the schematics here: Gold blocks indicate "any (suitable) block". For a cobblestone generator, "suitable" probably means "fireproof". Water and lava source blocks may be marked with "s" when there is possible confusion. Cobblestone or smooth stone appear only where they form. An "x" indicates a place to stand while mining the cobblestone.
A lava stream touching a water stream is the simplest type of generator. In a 10 block long trench with sources at either end, the cobble will form next to the lava. With a little more digging, you can manage this more compactly, and even get a current to wash the mined cobblestone away from the lava. This and the next design are easily expandable for multiplayer use.
The "From Below" generator is a small building with the generator proper on the roof. Putting the generator on the roof means very little cobblestone is lost to the lava, but it is a lot more work. This one too uses two lava streams.
Pistons can be used to automate the cobblestone generator and reduce the amount of cobblestone lost. Piston cobblestone generators work on the same principle as standard generators, but, rather than mining, a piston pushes the fresh cobblestone or stone out of the way, allowing the streams to touch once again. Piston cobblestone generators can be used both to create a large supply of cobblestone that the player can mine later, or to supply a self-repairing structure with blocks. The piston can be driven by a clock, or by a circuit to detect when a cobblestone block has appeared. The cobblestone will extend in a long line or pillar; if you don't want it to extend out to the full 13 blocks, you can "cap" it with any unpushable block. Furnaces will do fine, and you have plenty of cobblestone handy to make them.
Components of a piston generator
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 in front of the piston. It's generally based on a basic generator plan, with modifications for the piston and redstone.
A clock circuit or block detector, driving a piston. This part generates a signal to drive the piston that pushes fresh cobblestone out. The clock period can be chosen to minimize excessive piston movement.
A block detector is simply a circuit from a power source to the piston, passing through redstone repeaters before and after the spot where the cobblestone will appear. When the block does appear, the repeaters can push current through it to trigger the piston.
A clock generates its signal repeatedly at fixed intervals. Any of the basic repeater clocks will do perfectly well, but you want a total period of at least 7 or 8 (that is, a 4-clock or longer).
The core piston itself is usually non-sticky, but some block-detector CSG designs have a sticky piston with a transparent (non-conducting) block.
Optional secondary pistons. Since pistons can only push a maximum of 12 blocks, the core will only produce at most 13 cobblestone blocks at a time. This can be greatly increased with secondary pistons that guide the row of cobblestone in other directions. Like the core piston, the idea is to get the fresh cobblestone out of the way so that more can be created. A line of secondary pistons may also be used to move the blocks directly into self-repairing structures. Secondary pistons can be triggered by the same clock or detection circuit as the core piston, but this can be noisy if there are many of them. Alternatively, they can get their own clock or detection circuit.
Examples of piston cobblestone generators
The first design uses a redstone clock drives a piston which pushes out the generated cobblestone from a basic core. The second uses a block-detection circuit, and pushes the cobblestone upwards.
These advanced generator designs consistently produce four cobblestone blocks on every fourth piston cycle. The blocks are pushed upwards, negating any chance of the cobblestone burning from touching lava.
Cobblestone Quad-piston "Factory":
Lava flowing into water from above creates smooth stone. Stone can be mined slightly faster than cobblestone, and it can also be collected as stone using a pickaxe with the Silk Touch enchantment. Using smooth stone also gives self-repairing structures a different, more natural look.
Smooth stone generators are rarely designed without pistons, as lava needs to be directly above the stone generated. Lava must flow down into flowing water in front of the piston. As with cobblestone generators, a single-piston design can only make a row of stone up to 13 blocks long.
Examples of a Smooth Stone Generator:
As it is faster to mine, it can be more time efficient to use a smooth stone generator over a cobblestone one.
This will create 24 blocks of stone at the press of a button. And because it runs by lava flowing over water, (not the other way around) you do not need to worry about the lava source block becoming obsidian.
Start by creating the structure where the stone will form.
Find a place to build your farm. It should have a part that is exactly 4 blocks high and has at least 4 blocks of space in either direction.
In your chosen 4-block area, place a dispenser facing down on the ceiling.
On the floor below the dispenser, place two blocks on top of each other. The block to use depends on the type of pickaxe you plan to use.
If you plan to use an iron or diamond pickaxe, the blocks should be obsidian. Otherwise, you can also use an ore besides coal or nether quartz, or you can use a mineral block besides coal, quartz, or redstone. Iron ore and gold ore can be obtained without the silk touch enchantment.
If you plan to use a stone pickaxe, exclude iron ore, lapis lazuli ore, block of iron, or Lapis lazuli blocks.
Place fence or nether brick fence 4 blocks away from your 2-block tower. These will be the corners.
Connect the corners by placing fence or nether brick fence in a diagonal line towards adjacent fence posts.
Place water source blocks on the floor (not the two-block tower)
Finally, put a lava bucket in the dispenser.
You also need a redstone circuit to make the dispenser place the lava and then retrieve it. To create it, you will need to be above the future stone farm. The following steps explain how make a repeat circuit.
Place a sticky piston facing up.
Place an opaque block (The page "opacity" has a list of transparent blocks, which are the blocks you should not use.) on top of the sticky piston (the sticky piston should move the block. See the page "piston" for blocks where the sticky piston will do something else if you're not sure).
Place some redstone dust. The redstone wire should connect to the dispenser. Connect this wire to a block with a button attached (Make sure this block is not directly above your future stone farm. This way, you can easily press the button outside the stone farm when you want to make stone.)
For the block on the sticky piston to transmit the redstone signal, there needs to be a repeater next to the block facing away.
Place redstone dust in front of the repeater and set the repeater to a 4 tick delay.
Place a repeater facing awyay from the redstone dust. This repeater should face a different direction than the previously placed repeater.
Repeat steps 5 and 6 until you have 4 repeaters. Make sure that none of the repeaters are facing the same direction. If done correctly, you will not be able to place redstone in front of the last repeater. It should still be a 4-tick delay, however.
Connect the redstone between the last 2 repeaters to another circuit, which will lead to the sticky piston. Include 5 repeaters and set 4 of them to a 4-tick delay. Make sure it is disconnected from any other redstone.
Now your stone farm is complete. To make stone, simply press the button.
Compact Cobblestone Generator
Here's how to build a compact cobblestone generator:
1. Dig a trench four blocks long.
2. Dig down one in one of the middle blocks of the trench.
3. Put water in the smallest side.
4. Put lava in the other side.
5. Mine cobblestone!
More video tutorials/examples
AFK design which allows you to put something heavy on your mouse and go away from your keyboard. After your pickaxe breaks, a new one will be dispensed.