Granite is a possibly next upcoming material.  Jeb has mentioned that granite will be craftable "likely from some kind of Cobblestone+Quartz combination". He has also mentioned that he is not sure whether or not granite will generate naturally.

Most likely, there will be two versions of granite blocks, "regular" granite and smooth granite.

The very first image uploaded of a granite block. Uploaded by Jeb https://twitter.com/jeb_/status/413240263906443264

The first and so far only screenshot of smooth granite.

Post your comments on this new block down below,

Can you mine it with iron?

What else can you make from it?

Is it blast resistant?

Can it be coloured?