igneous

Basalt with Quartz/Quartzite Veins

Aphanitic Mafic Volcanic Rock with Siliceous Infillings

Hardness: 6-7 (Mohs scale), Color: Dark grey to black matrix with tan/white veins, Luster: Dull/Earthy matrix with Vitreous veins, Structure: Fine-grained (aphanitic) matrix, Specific Gravity: 2.8-3.0

Identified May 9, 2026More igneous →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava at the surface. The linear veins formed later as hydrothermal fluids rich in silica filled fractures in the cooling rock and crystallized.

Uses & applications

Largely used as crushed stone for aggregate in construction, road base, and railroad ballast. This specific piece is a river-worn decorative specimen.

Geological facts

Basalt is the most common rock type in Earth's crust and makes up the entirety of the ocean floor. The veins represent ancient 'scars' where the rock cracked and healed through geological fluid circulation.

Field identification & locations

Identified by its heavy weight, dark color, and the presence of prominent protruding veins (which are harder and erode slower than the host rock). Commonly found in volcanic regions and riverbeds.

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