igneous

Granite (Weathered)

Grano-diorite / Granite (SiO2 rich intrusive rock)

Hardness: 6-7 Mohs; Color: Speckled tan, grey, and black due to oxidation; Luster: Dull to vitreous; Crystal structure: Phaneritic (visible interlocking crystals); Cleavage: Distinct in feldspars, none in quartz.

Hardness: 6-7 Mohs
Color: Speckled tan, grey, and black due to oxidation
Luster: Dull to vitreous

Identified April 12, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling of silica-rich magma deep underground (plutonic). This specific sample shows significant surface weathering and iron oxidation (limonite staining), indicating it was exposed to the elements for a long period.

Uses & applications

Used extensively in construction as dimension stone, countertops, road base (crushed), and as architectural veneer.

Geological facts

Granite makes up a large portion of the Earth's continental crust. Because of its hardness, it survives erosion better than surrounding rocks, often forming the cores of major mountain ranges.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and interlocking crystal texture where grains do not rub off like sand. Found worldwide in mountainous regions and shield areas.

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

mineral

Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral