igneous

Granodiorite Pebble

Granodiorite (Intermediate intrusive igneous rock)

Hardness: 6-7 on Mohs scale; Color: Salt-and-pepper (speckled grey, white, and black); Luster: Dull to phaneritic (visible crystals); Crystal Structure: Granular/Holocrystalline; Cleavage: Poor; Specific Gravity: 2.6-2.7

Hardness: 6-7 on Mohs scale
Color: Salt-and-pepper (speckled grey, white, and black)
Luster: Dull to phaneritic (visible crystals)

Identified March 18, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling of silica-rich magma beneath the Earth's surface (plutonic). This specific specimen has been rounded through fluvial or glacial erosion, typically occurring over millions of years.

Uses & applications

Used primarily in construction as crushed stone or road base. Larger deposits are used for architectural stone and countertops. This specific smooth specimen is popular for decorative landscaping or as a 'worry stone'.

Geological facts

Granodiorite is the most common rock of the Earth's continental crust. The famous Rosetta Stone was carved from a slab of granodiorite.

Field identification & locations

Identify by its 'salt and pepper' appearance and visible interlocking crystals. It contains more plagioclase feldspar than orthoclase. Commonly found in riverbeds, glacial tills, and mountainous batholiths worldwide.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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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)

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Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

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

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Magnetite

Magnetite (Fe3O4)

mineral