Minecraft wiki entry for Pre-flattening, associated text: Mushroom blocks consist of the same blocks throughout their structure, the data value of each block decides the texture. The default texture on all sides is porous flesh. The cap texture can be either the brown mushroom or red mushroom texture, the textures for porous and stem sides are identical. Although data values 11-13 are unused they have the same texture as data value 0 as placeholders (to keep people from destroying their maps).