igneous

Drill Core (Basalt or Andesite)

Volcanic porphyry (mafic to intermediate)

Hardness: 5-7 Mohs; Color: dark grey to black with light crystalline phenocrysts; Luster: dull to earthy; Structure: fine-grained (aphanitic) matrix; Specific Gravity: 2.7-3.0

Hardness: 5-7 Mohs
Color: dark grey to black with light crystalline phenocrysts
Luster: dull to earthy

Identified May 27, 2026More igneous →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 5-7 Mohs; Color: dark grey to black with light crystalline phenocrysts; Luster: dull to earthy; Structure: fine-grained (aphanitic) matrix; Specific Gravity: 2.7-3.0

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. This specific specimen is a core sample extracted from deep underground via diamond drilling for mineral exploration.

Uses & applications

Used in geological surveying, mineral exploration, and mining to sample subsurface lithology and identify ore-bearing zones.

Geological facts

The markings on the rock (C-423, Caranundra) indicate it is a sample from a specific drill hole. Drill cores provide the only direct sight into the Earth's crust at great depths.

Field identification & locations

Identify in the field by its cylindrical shape and core-drilling marks. Commonly found near active or historical mining exploration sites in volcanic belts.

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

Dalmatian Jasper

Aplite with Arfvedsonite inclusions

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