igneous

Diabase (Greenstone)

Diabase (also known as Dolerite)

Hardness: 6-7 (Mohs scale), Color: Dark grey to greenish-black with iron-oxidized pitting, Luster: Dull/Sub-vitreous, Crystal structure: Fine-to-medium grained phaneritic/ophitic, Specific Gravity: 2.7-3.3

Identified May 16, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the cooling of mafic magma in shallow intrusive bodies like dikes or sills. The greenish tint often suggests low-grade metamorphism (greenschist facies) or chloritization of primary minerals over millions of years.

Uses & applications

Commonly used as crushed stone for road construction (riprap), high-quality railroad ballast, and decorative building stone or monuments.

Geological facts

Diabase is the primary rock type of the famous Hudson River Palisades in New York and New Jersey. It is chemically similar to basalt but cooled more slowly underground.

Field identification & locations

Identified by its dense, 'heavy' feel relative to its size and dark greenish-grey weathered surface with orange-brown iron spots. Often found in riverbeds or glacial tills in volcanic regions.

Other igneous specimens

See all

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