igneous

Granite Pebble

Phaneritic plutonic rock (dominated by Quartz, Feldspar, and Mica)

Hardness: 6-7 (Mohs scale); Color: Mottled grey, white, and pink; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Individual minerals vary (feldspar has 2 directions); Specific Gravity: 2.63-2.75

Hardness: 6-7 (Mohs scale)
Color: Mottled grey, white, and pink
Luster: Vitreous to dull

Identified May 27, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of silica-rich magma beneath the Earth's surface. These rocks can be hundreds of millions to billions of years old and are typically found in the continental crust.

Uses & applications

A cornerstone of construction, used for countertops, monuments, paving stones, and as crushed stone for aggregate in road building.

Geological facts

Granite makes up a large portion of the Earth's continental crust. Over time, it is exposed at the surface through erosion and uplift, often forming massive domes like those seen in Yosemite National Park.

Field identification & locations

Identify in the field by its speckled 'salt and pepper' appearance and visible interlocking crystals. It is extremely common in mountain ranges and glacial deposits (tills) worldwide.

Other igneous specimens

See all

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous

Dalmatian Jasper

Aplite with Arfvedsonite inclusions

igneous

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral