igneous

Granite

Granite (Mainly Quartz, Alkali Feldspar, and Plagioclase)

Hardness: 6-7 Mohs; Color: Salt and pepper (pink, gray, black); Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained visible crystals); Specific Gravity: 2.63 - 2.75

Hardness: 6-7 Mohs
Color: Salt and pepper (pink, gray, black)
Luster: Dull to vitreous

Identified April 7, 2026More igneous →

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Physical properties

Hardness: 6-7 Mohs; Color: Salt and pepper (pink, gray, black); Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained visible crystals); Specific Gravity: 2.63 - 2.75

Formation & geological history

Formed from the slow crystallization of magma below Earth's surface. It is a plutonic rock found in continental crust and can range in age from Precambrian to Cenozoic.

Uses & applications

Construction material for countertops, floor tiles, paving stones, curbing, monuments, and as crushed stone for road base.

Geological facts

Granite is one of the hardest and most durable rocks on Earth, which is why it has been used for ancient monuments like the Great Pyramid of Giza. It makes up the core of most mountain ranges.

Field identification & locations

Identify in the field by its coarse crystalline texture and visible grains of quartz (glassy) and feldspar (blocky/opaque). It is widely found in continental mountain ranges and old shield areas.

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