Granitoid (Granite/Diorite)

Physical Properties

Hardness: 6-7 (Mohs scale); Color: Salt and pepper (white/light grey with dark speckles); Luster: Dull to sub-vitreous; Crystal structure: Phaneritic (coarse-grained crystals visible to the naked eye); Cleavage: None (fractures irregularly); Specific gravity: 2.6-2.7.

Formation & Geological History

Formed through the slow cooling and crystallization of magma beneath the Earth's surface (intrusive). These rocks can date back to various geological eras, commonly found in the cores of mountain ranges and ancient continental shields.

Uses & Applications

Used extensively in construction (as crushed stone or dimension stone), countertops, monuments, and as decorative landscaping boulders.

Geological Facts

Granite makes up a large portion of the Earth's continental crust. El Capitan in Yosemite National Park is one of the most famous massive exposures of granite in the world.

Field Identification & Locations

Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. It is ubiquitous in glacial til deposits and riverbeds across North America and Europe. For collectors, it is a primary example of intrusive igneous textures.

Identified on: 4/19/2026

Mode: Standard