igneous

Granodiorite

Phaneritic intrusive igneous rock (intermediate composition)

Phaneritic texture (visible grains), hardness of 6-7 on Mohs scale, salt-and-pepper appearance with grey and white tones, dull to vitreous luster, composed mainly of plagioclase feldspar, quartz, and minor dark minerals like biotite or hornblende.

Identified June 4, 2026More igneous →

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Physical properties

Formation & geological history

Formed by the slow cooling of magma beneath the Earth's surface in continental crust environments, typically within batholiths above subduction zones. These specimens often date from various mountain-building eras over hundreds of millions of years.

Uses & applications

Commonly used as crushed stone for road construction, paving, and occasionally as structural stone or high-quality aggregate in concrete. It can also be polished for architectural use like countertops.

Geological facts

The famous Rosetta Stone was originally identified as granite but was later correctly identified as being carved from a slab of granodiorite. It is chemically intermediate between granite and diorite.

Field identification & locations

Identify by looking for a speckled 'salt and pepper' appearance with more grey plagioclase than pink orthoclase feldspar. River-worn specimens like this are found in glacial till and riverbeds globally.

Other igneous specimens

See all

Granite

Igneous

Granite

Igneous

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dalmatian Jasper

Aplite with Arfvedsonite inclusions

igneous

Magnetite

Iron(II,III) oxide (Fe3O4)

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