igneous

Granodiorite

Granodiorite (containing Plagioclase, Quartz, and K-feldspar)

Hardness: 6-7 on Mohs scale. Color: Grayish-white to light gray with orange/brown iron oxide weathering. Luster: Dull to phaneritic (visible crystals). Crystal structure: Massive phaneritic grains with a granular texture. Cleavage: Poor (fractures unevenly).

Hardness: 6-7 on Mohs scale
Luster: Dull to phaneritic (visible crystals)

Identified April 12, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow cooling of magma deep beneath the Earth's surface (intrusive). Most common in volcanic arcs and mountain-building regions (subduction zones). It belongs to the Phaneritic Plutonic rock family.

Uses & applications

Commonly used as crushed stone for road construction, landscaping, and building foundations. High-quality slabs can be polished and used for countertops and floor tiles, often sold under the commercial name 'granite'.

Geological facts

Granodiorite is the most common rock type in the continental crust and constitutes the majority of the famous Yosemite National Park batholith. The Rosetta Stone was carved from a slab of granodiorite.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance (mixture of light and dark minerals) where light minerals are dominated by plagioclase rather than orthoclase. Commonly found in mountainous terrains and glacial deposits. This specimen shows significant orange iron-oxide staining common in surface weathering.

Other igneous specimens

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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

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Blue Apatite

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

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Magnetite

Magnetite (Fe3O4)

mineral