Granite

Hardness: 6-7 on Mohs scale. Color: Typically light-colored, but can range from white, pink, gray, to black, depending on mineral composition. Often speckled. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained). Cleavage: Varies by mineral components (e.g., feldspar shows cleavage). Specific Gravity: 2.6 – 2.7 g/cm³.

Granite forms from the slow crystallization of magma below Earth's surface (intrusive igneous). It cools slowly, allowing large crystals to form. It is often found in mountain ranges and continental crust, forming batholiths and laccoliths. Geological Age: Ranges widely, from Precambrian to Cenozoic, depending on the specific intrusion and location, with many major granite formations dating to continental collisions hundreds of millions to billions of years ago.

Industry/Construction: Widely used as a construction material (countertops, flooring, building facades, paving), due to its durability, strength, and aesthetic appeal. Jewelry: Rarely used as a gemstone itself, but polished slabs are used in decorative items and monuments. It is also used as crushed stone in road construction and as an aggregate in concrete.

Granite makes up a significant portion of the Earth's continental crust. El Capitan and Half Dome in Yosemite National Park are famous examples of granite formations. Many of the oldest rocks on Earth are granitic, providing insights into early continental formation.

In the field, granite is identified by its coarse-grained texture and visible interlocking crystals of quartz (glassy, gray), feldspar (white, pink, or red, often blocky), and dark minerals like biotite mica (black flakes) or hornblende (dark elongated crystals). It is commonly found in shield areas, the cores of mountain ranges, and large igneous intrusions (batholiths) worldwide. Tips for collectors: Look for freshly broken surfaces to best observe the mineral grains. Its resistance to weathering means it can often be found as resistant boulders or outcrops.