igneous
Granite
Granite (phaneritic felsic intrusive rock)
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (gray, white, black, with some tan/brown weathering). Luster: Dull to vitreous depends on mineral face. Crystal structure: Phaneritic (visible crystals of quartz, feldspar, and biotite). Cleavage: Varies by mineral component.
- Hardness
- 6-7 on Mohs scale
- Luster
- Dull to vitreous depends on mineral face
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (gray, white, black, with some tan/brown weathering). Luster: Dull to vitreous depends on mineral face. Crystal structure: Phaneritic (visible crystals of quartz, feldspar, and biotite). Cleavage: Varies by mineral component.
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface. High in silica and alkali oxides. This specific specimen shows signs of secondary mineral veining (likely quartz) and iron oxide staining from environmental weathering.
Uses & applications
Widely used in construction for dimension stone, countertops, floor tiles, and as crushed stone for road base. Its durability makes it ideal for monuments and memorials.
Geological facts
Granite makes up a large part of the Earth's continental crust. Unlike oceanic crust which is primarily basalt, the continents 'float' because granite is less dense. The white vein running through this sample represents a later-stage hydrothermal injection where mineral-rich water filled a fracture.
Field identification & locations
Identify by its interlocking granular texture where crystals are visible to the naked eye. Look for the 'salt and pepper' appearance. Common globally in mountain ranges and shields. Collectors look for unique inclusions or large 'megacrysts' of feldspar.
