igneous

Granite Pebble

Felsic Intrusive Igneous Rock (composed of Quartz, Alkali Feldspar, and Plagioclase)

Hardness: 6-7 on Mohs scale; Color: Mottled grey, white, and dark minerals; Luster: Dull (weathered) to vitreous (on fresh breaks); Crystal structure: Phaneritic (visible interlocking crystals); Specific gravity: 2.63 - 2.75.

Hardness: 6-7 on Mohs scale
Color: Mottled grey, white, and dark minerals
Luster: Dull (weathered) to vitreous (on fresh breaks)

Identified February 24, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling of silica-rich magma deep underground. This specimen appears water-worn, smoothed by alluvial or glacial transport processes after being exposed by erosion.

Uses & applications

Crushed stone for road base, Dimension stone for countertops and monuments, and architectural aggregate. This specific pebble size is often used in landscaping and xeriscaping.

Geological facts

Granite makes up a large part of the Earth's continental crust. It is essentially the 'signature' rock of our planet, as it is found in such abundance only on Earth compared to other planets in our solar system.

Field identification & locations

Identify by its 'salt and pepper' appearance and hardness (it will scratch glass). Commonly found in riverbeds, glacial tills, and mountain ranges. Collectors should look for unique mineral inclusions like tourmaline or garnet within the matrix.

Other igneous specimens

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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)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral