igneous

Granite (Granitic Pegmatite/Porphyry)

Felsic intrusive igneous rock (Quartz, Feldspar, Mica composition)

Hardness: 6-7 Mohs; Color: Tan, white, grey, and black speckles; Luster: Vitreous to pearly; Crystal structure: Phaneritic (large visible crystals), primarily hexagonal quartz and monoclinic/triclinic feldspars; Specific gravity: 2.63 to 2.75.

Hardness: 6-7 Mohs
Color: Tan, white, grey, and black speckles
Luster: Vitreous to pearly

Identified April 8, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below Earth's surface. This specimen shows a porphyritic or pegmatitic texture, indicating a multi-stage cooling process where some crystals grew larger than the surrounding matrix.

Uses & applications

Construction (countertops, flooring), monuments, curbing, and crushed stone for road aggregate. Highly valued for durability and resistance to abrasion.

Geological facts

Granite makes up a large portion of the Earth's continental crust. Over long periods of time, the radioactive decay of uranium in granite can lead to the accumulation of radon gas in buildings built over granitic bedrock.

Field identification & locations

Identify in the field by the 'salt and pepper' appearance and hardness (it will scratch glass). It is commonly found in the cores of mountain ranges and stable continental shields (cratons). Check for interlocking crystalline textures rather than layers.

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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)

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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