Cobblestone



Cobblestone is one of the most common blocks after Stone is mined with any pickaxe. Cobblestone can be smelted back into Stone blocks in a furnace with a 1:1 ratio. Common uses for Cobblestone include producing scrap in a Recycler or using the EMC value of 1 to make less expensive items in the Energy Condenser.

Usage
Cobblestone has many uses in Tekkit. One of them is for making stone Gears, the second tier of BuildCraft gears.

Cobblestone is also used to make a Macerator. Cobblestone can then be macerated to produce sand.

Read more
http://www.minecraftwiki.net/wiki/Cobblestone