Basalt is a mafic extrusive igneous rock formed from the rapid cooling of low-viscosity lava flows. It is characteristically dark-colored and fine-grained, often displaying columnar jointing or vesicular textures due to gas bubbles trapped during solidification.

Hardness

Mohs

Luster

Dull

Streak

White

Transparency

Opaque

igneouscommon

Basalt

Hardness: 6
Luster: Dull
Streak: White
Transparency: Opaque

Is this basalt?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch basalt with a known reference. Basalt sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Basalt leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Basalt typically shows a dull luster.
4
Match the color range
Compare against the expected color range: black, dark gray, dark green, brown.
5
Look at form & habit
Typical habit: aphanitic to porphyritic.

Often confused with

Basalt vs. its common look-alikes — and how to tell them apart in the field.

How to tell apart: Streak differs — Basalt leaves white, Gabbro leaves none; luster reads dull on Basalt and vitreous on Gabbro.

Compare →

Often found alongside basalt

Minerals reported to co-occur with basalt. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Mohs hardness: 6
Density: 2.8-3.0 g/cm³
Colors: Black Dark Gray Dark Green Brown
Streak: White
Luster: Dull
Transparency: Opaque
Crystal habit: Aphanitic to Porphyritic
Cleavage: None
Rarity: Common
Uses: Industrial, Construction, Decorative
Host rock: Volcanic Terrains
Typical price: $1-20 for specimens

Where rockhounds find basalt

1 mapped spots

Classic worldwide localities

Iceland
Hawaii, USA
Giant's Causeway, Northern Ireland
Columbia River Plateau, USA
Deccan Traps, India

Field-hunting tip

Look in volcanic terrains country — that is the host setting where basalt typically forms. If you start seeing olivine, plagioclase, pyroxene in float, you are in the right ground. Field specimens usually show a aphanitic to porphyritic habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in California — start trip planning there.

Browse 1 U.S. spots for basalt →

Common questions

How do you identify basalt?+

Mohs hardness is 6. It typically shows a dull luster. The streak is white. Common colors include black, dark gray, dark green, brown.

Where is basalt found?+

Notable localities include Iceland; Hawaii, USA; Giant's Causeway, Northern Ireland; Columbia River Plateau, USA; Deccan Traps, India.

Can I find basalt in the United States?+

RockHoundR maps 1 basalt rockhounding spots across 1 U.S. states — the top states are California.

How much is basalt worth?+

Typical asking prices fall in the range of $1-20 for specimens. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like basalt?+

Basalt is most often confused with Andesite, Gabbro. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with basalt?+

Basalt commonly co-occurs with Olivine, Plagioclase, Pyroxene, Magnetite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does basalt form in?+

Basalt typically forms in volcanic terrains. Working float back to the host body is the standard way to chase a fresh occurrence.

What is basalt used for?+

Basalt is used in industrial, construction, decorative.

Find basalt on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.