Photographed by Michael P. Klimetz
Granophyre is an igneous rock that contains quartz and alkali feldspar in characteristic angular intergrowths. The resulting texture is henceforth called granophyric. Granophyric 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. Granophyres typically are intrusive rocks that crystallized at shallow depths, and many have compositions similar to those of granites. A common occurrence of granophyre is within layered igneous intrusions dominated by rocks with compositions similar to that of gabbro. In such occurrences, the granophyre may form as an end product of fractional crystallization of a parent mafic magma, or by melting of rocks into which the mafic magma was emplaced, or by a combination of the two processes.