igneous

Crushed Stone (Likely Granite or Diabase)

Intrusive Igneous Rock (Granitoid/Gabbroid)

Hardness: 6-7 Mohs; Color: Salt-and-pepper (gray, white, black); Luster: Dull to vitreous; Crystal structure: Phaneritic (visible interlocking crystals); Specific gravity: 2.6-3.0

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

Identified March 29, 2026More igneous →

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Physical properties

Hardness: 6-7 Mohs; Color: Salt-and-pepper (gray, white, black); Luster: Dull to vitreous; Crystal structure: Phaneritic (visible interlocking crystals); Specific gravity: 2.6-3.0

Formation & geological history

Formed from the slow cooling of magma deep beneath the Earth's surface (plutonic). These rocks typically date from the Precambrian to Cenozoic eras, found in continental crust and mountain belts.

Uses & applications

Primarily used as construction aggregate, road base, driveway gravel, and railroad ballast due to its high compressive strength and durability.

Geological facts

Granite makes up a large portion of the continental crust. Diabase (a darker variant often used in crushed stone) is the primary rock of the famous Palisades along the Hudson River.

Field identification & locations

Identify by its interlocking crystalline texture and lack of layering (foliation). Commonly found in quarries and used globally in domestic landscaping and urban infrastructure.

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