Diorite is a confirmed block that was released in 1.8 and 0.9 for Minecraft Pocket Edition. It closely resembles Granite and Gravel.
Normal Diorite can be found everywhere underground in large chains. It is usually exposed on the surface in Extreme Hills, but will generate in other biomes too. You can find Diorite in the new 0.9.0 Minecraft Pocket Edition update.