igneous

Granite (Weathered)

Granite (Felsic Plutonic Rock)

Hardness: 6-7 on Mohs scale; Color: Gray, pink, reddish-brown showing iron oxide staining; Luster: Pearly to Vitreous (when fresh), Dull (when weathered); Structure: Coarse-grained/Phaneritic; Specific Gravity: 2.6-2.7

Hardness: 6-7 on Mohs scale
Color: Gray, pink, reddish-brown showing iron oxide staining
Luster: Pearly to Vitreous (when fresh), Dull (when weathered)

Identified March 1, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below Earth's surface. This specific specimen shows chemical weathering and oxidation (rusting) of iron-bearing minerals like biotite or hornblende.

Uses & applications

Primarily used in construction for crushed stone, road base, and dimension stone for countertops and monuments. Weathered granite is often used as decomposed granite (DG) for walkways.

Geological facts

Granite makes up the majority of Earth's continental crust. Over millions of years, the softer minerals in granite like feldspar weather into clay, while the harder quartz grains become sand.

Field identification & locations

Identify in the field by looking for a 'salt and pepper' appearance with visible interlocking crystals of quartz and feldspar. Found globally in mountainous regions and shields like the Canadian Shield. These weathered samples are common in topsoil and riverbeds.

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