Wikia

Clay (Block)
Tool	<img alt="Grid Shovel" src="data:image/gif;base64,R0lGODlhAQABAIABAAAAAP///yH5BAEAAAEALAAAAAABAAEAQAICTAEAOw%3D%3D" width="32" height="32" data-image-name="Grid Shovel.png" data-image-key="Grid_Shovel.png" data-src="http://images1.wikia.nocookie.net/__cb20121201073756/thetekkit/images/e/e2/Grid_Shovel.png" class="lzy lzyPlcHld" onload="if(typeof ImgLzy=="object"){ImgLzy.load(this)}" /><noscript><img alt="Grid Shovel" src="http://images1.wikia.nocookie.net/__cb20121201073756/thetekkit/images/e/e2/Grid_Shovel.png" width="32" height="32" data-image-name="Grid Shovel.png" data-image-key="Grid_Shovel.png" />
Stackable	Yes (64)
Data Value	82
EMC Value	256
Mod Included	Vanilla

Clay is a vanilla block found close to or under water. When one clay block is destroyed it drops four clay balls, and each ball can either be made back into one block, macerated to give two clay dust, or put in a furnace to craft one Brick.