igneous

Granite Cobble

Phaneritic Felsic Igneous Rock (primarily Quartz, Feldspar, and Mica)

Hardness: 6-7 Mohs; Color: Tan/buff exterior with white/grey interior; Luster: Dull (weathered) to Vitreous (internal); Crystal Structure: Phaneritic (visible grains); Specific Gravity: 2.6-2.7

Hardness: 6-7 Mohs
Color: Tan/buff exterior with white/grey interior
Luster: Dull (weathered) to Vitreous (internal)

Identified February 19, 2026More igneous →

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Physical properties

Hardness: 6-7 Mohs; Color: Tan/buff exterior with white/grey interior; Luster: Dull (weathered) to Vitreous (internal); Crystal Structure: Phaneritic (visible grains); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through slow crystallization of magma below Earth's surface. This specimen has been rounded by fluvial activity (river or stream transport) and exhibits a weathered outer rind (patina) due to long-term exposure to the elements.

Uses & applications

Commonly used in crushed form for road construction, as architectural veneer, or as decorative landscaping stones.

Geological facts

Granite comprises a significant portion of Continental Crust. This specific round shape is the result of 'abrasion'—the geological process where stones collide in moving water, wearing down sharp edges over centuries.

Field identification & locations

Identify by its coarse-grained 'salt and pepper' texture and its inability to be scratched by a steel knife. Common in riverbeds, glacial tills, and mountainous regions worldwide.

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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