Granitoid (Granite/Gneiss)

Physical Properties

Hardness: 6-7 Mohs; Color: Gray, white, and black speckled (salt and pepper); Luster: Dull to vitreous; Structure: Phaneritic (visible grains), showing slight foliation or banding; Composition: Quartz, Plagioclase feldspar, Biotite mica.

Formation & Geological History

Formed through the slow cooling of silica-rich magma deep underground. This specific specimen shows slight alignment of minerals (foliation), suggesting it may have undergone low-grade regional metamorphism during mountain-building events.

Uses & Applications

Used widely in construction for countertops, floor tiles, and as crushed stone for road base. Also used for monuments and decorative landscaping.

Geological Facts

Granite is the most common rock found in the Earth's continental crust. It is incredibly durable and resistant to weathering, which is why it is used for memorials that must last centuries.

Field Identification & Locations

Identify in the field by its hardness (will scratch glass), granular texture, and 'salt and pepper' appearance. Found globally in the cores of mountain ranges and ancient shields like the Canadian Shield.

Identified on: 4/16/2026

Mode: Standard