Granophyre

Granophyre (/ˈɡrænəˌfaɪər, -noʊ-/ GRAN-ə-fyr; from granite and porphyry) is a subvolcanic rock that contains quartz and alkali feldspar in characteristic angular intergrowths such as those in the accompanying image.

The texture is called granophyric. The texture can be similar to micrographic texture and to the coarser graphic intergrowths of quartz and alkali feldspar common in pegmatite. These textures document simultaneous crystallization of quartz and feldspar from a silicate melt at the eutectic point, perhaps in the presence of a water-rich phase. They may also be formed by crystallization when the magma is significantly undercooled, not necessarily under eutectic conditions.