igneous
Coarse-grained Granite
Granitoid (KAlSi3O8 + SiO2 + NaAlSi3O8)
Hardness: 6-7 on Mohs scale; Color: Phaneritic mixture of pink/tan (potassium feldspar), white (plagioclase), and gray/translucent (quartz); Luster: Vitreous to pearly; Crystal structure: Crystal grains are easily visible to the naked eye (phaneritic texture).
- Hardness
- 6-7 on Mohs scale
- Luster
- Vitreous to pearly
Identified More igneous →
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Phaneritic mixture of pink/tan (potassium feldspar), white (plagioclase), and gray/translucent (quartz); Luster: Vitreous to pearly; Crystal structure: Crystal grains are easily visible to the naked eye (phaneritic texture).
Formation & geological history
Formed through the slow cooling of silica-rich magma deep underground (plutonic formation) over millions of years. This specimen shows large interlocking crystals characteristic of intrusive igneous processes.
Uses & applications
Used extensively in construction for countertops, floor tiles, and gravel. It is also a primary material for monuments, bridges, and paving due to its durability and resistance to weathering.
Geological facts
Granite makes up a large portion of the Earth's continental crust. It is often found in the roots of mountain ranges where erosion has exposed the deep-seated 'plutons'. Famous examples include the peaks of Yosemite and the White Mountains.
Field identification & locations
Identify in the field by looking for a 'salt and pepper' or multi-colored speckled appearance with hard, scratch-resistant mineral grains. Commonly found in mountainous regions or glacial deposits. Collectors look for unique inclusions or rare accessory minerals like tourmaline.
