igneous

Granite (River-worn Cobble)

Phaneritic Felsic Igneous Rock (primarily Quartz, Potassium Feldspar, and Plagioclase)

Hardness: 6-7 Mohs scale. Color: Mottled pink (orthoclase feldspar), white (plagioclase), and black (biotite/amphibole). Luster: Dull to vitreous. Structure: Phaneritic (visible crystals). Cleavage: Varies by mineral constituent. Specific Gravity: 2.63 to 2.75.

Hardness: 6-7 Mohs scale
Luster: Dull to vitreous

Identified February 19, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow cooling of silica-rich magma deep underground (plutonic). This specific specimen shows significant rounding, indicating it was transported and abraded by water in a high-energy environment like a river or glacial stream.

Uses & applications

Used extensively in construction (countertops, flooring, monuments), as crushed stone for road base, and as decorative landscaping (river rocks).

Geological facts

Granite makes up a large portion of the Earth's continental crust. Because of its hardness and resistance to weathering, it often survives long-distance transport in rivers while softer rocks disintegrate.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance with pink/orange hues and interlocking crystal texture. Common in continental shield areas or mountainous regions. Collectors look for unique mineral inclusions or high-polish potential.

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

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral