igneous
Granite / Diorite (Granitoid)
Granitoid rock (composed mainly of Quartz, Feldspar, and Amphibole/Biotite)
Hardness 6-7 on Mohs scale. Speckled salt-and-pepper appearance with white/grey feldspar and quartz alongside dark mafic minerals (hornblende, biotite). Phaneritic coarse-grained texture, vitreous to dull luster.
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Physical properties
Hardness 6-7 on Mohs scale. Speckled salt-and-pepper appearance with white/grey feldspar and quartz alongside dark mafic minerals (hornblende, biotite). Phaneritic coarse-grained texture, vitreous to dull luster.
Formation & geological history
Formed by the slow crystallization of magma deep beneath the Earth's surface (plutonic igneous rock). Can range in age from ancient Precambrian to Cenozoic.
Uses & applications
Extensively used in construction, building facades, counter tops, monuments, paving stones, and aggregate material.
Geological facts
The black and white speckled pattern of diorite and granite makes it one of the most recognizable rock types. Ancient Egyptians frequently carved durable statues and obelisks from granite and diorite.
Field identification & locations
Identify by its interlocking visible mineral grains of contrasting light (feldspar, quartz) and dark (biotite, amphibole) colors. Extremely common in continental crust worldwide.
