igneous

Granitoid (Granitic Rock)

Granitoid (Quartzo-feldspathic plutonic rock)

Hardness: 6-7 on Mohs scale; Color: Salt and pepper appearance with shades of white, gray, and tan; Luster: Dull to vitreous (on crystal faces); Crystal structure: Phaneritic (visible interlocking grains); Composition: Primarily quartz, feldspar, and minor biotite/hornblende.

Hardness: 6-7 on Mohs scale
Luster: Dull to vitreous (on crystal faces)

Identified April 7, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow cooling and crystallization of silica-rich magma deep within the Earth's crust (plutonic formation). These rocks typically date from the Precambrian to Cenozoic eras.

Uses & applications

Used widely in construction (crushed stone, aggregate) and as dimension stone for countertops and monuments. Also valuable for studying crustal evolution.

Geological facts

Granite is the most common rock found in the continental crust and forms the core of many mountain ranges. Large crystals indicate the magma cooled extremely slowly over thousands of years.

Field identification & locations

Identify in the field by its interlocking 'crystalline' texture and lack of layering (foliation). It is extremely common in shield areas like the Canadian Shield or Appalachian region.

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