igneous

Granite (Weathered River Rock)

Plutonic Igneous Rock (primarily Quartz, Feldspar, and Mica)

Hardness: 6-7 Mohs scale; Color: Speckled white, grey, and green/black; Luster: Dull (weathered) to vitreous; Crystal structure: Phaneritic (coarse-grained); Cleavage: None (fractures unevenly); Specific gravity: 2.63 to 2.75

Hardness: 6-7 Mohs scale
Color: Speckled white, grey, and green/black
Luster: Dull (weathered) to vitreous

Identified March 14, 2026More igneous →

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Physical properties

Formation & geological history

Formed by the slow crystallization of magma below Earth's surface. This specific specimen shows signs of mechanical weathering and rounding, likely from fluvial (river) or glacial transport, making it an ancient material often hundreds of millions of years old.

Uses & applications

Used extensively in construction for countertops, floor tiles, and curbing. In its natural rounded form, it is often used for landscaping, drainage, or as decorative river stone.

Geological facts

Granite makes up the majority of the Earth's continental crust. Its name comes from the Latin 'granum', meaning a grain, in reference to its coarse-grained structure. It is one of the hardest and most durable natural stones available.

Field identification & locations

Identify in the field by its 'salt and pepper' speckled appearance and lack of layering (foliation). It will not scratch with a copper penny or steel knife easily. Commonly found in mountainous regions or riverbeds downstream from igneous outcrops.

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