Scoria is a highly vesicular, dark-colored volcanic rock formed from gas-rich basaltic lava. It is easily identified by its rough, bubbly appearance and low density, which often causes it to float on water initially, though it lacks the fine-grained, frothy texture of pumice.

Hardness

5-6

Mohs

Luster

Dull

Streak

White

Transparency

Opaque

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Scoria

Hardness: 5-6
Luster: Dull
Streak: White
Transparency: Opaque

Is this scoria?

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 scoria with a known reference. Scoria sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Scoria leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Scoria typically shows a dull luster.
4
Match the color range
Compare against the expected color range: black, dark gray, reddish brown, dark red.
5
Look at form & habit
Typical habit: vesicular.

Often confused with

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

How to tell apart: Streak differs, so Scoria leaves white, Vesicular Basalt leaves white to gray.

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Often found alongside scoria

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

All properties

Mohs hardness: 5-6
Density: 2.0-2.5 g/cm³
Colors: Black Dark Gray Reddish Brown Dark Red
Streak: White
Luster: Dull
Transparency: Opaque
Crystal habit: Vesicular
Cleavage: None
Rarity: Common
Uses: Landscaping, Road Construction, Filtration Media, Industrial Aggregate
Host rock: Volcanic Cones and Lava Flows
Typical price: $1-5 per pound as landscaping aggregate

Where rockhounds find scoria

Classic worldwide localities

Iceland
Italy
Hawaii
Mexico
United States

Field-hunting tip

Look in volcanic cones and lava flows country, the host setting where scoria typically forms. If you start seeing olivine, plagioclase, pyroxene in float, you are in the right ground. Field specimens usually show a vesicular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify scoria?+

Mohs hardness is 5-6. It typically shows a dull luster. The streak is white. Common colors include black, dark gray, reddish brown, dark red.

Where is scoria found?+

Notable localities include Iceland; Italy; Hawaii; Mexico; United States.

How much is scoria worth?+

Typical asking prices fall in the range of $1-5 per pound as landscaping aggregate. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like scoria?+

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

What minerals are found with scoria?+

Scoria commonly co-occurs with olivine, plagioclase, pyroxene. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does scoria form in?+

Scoria typically forms in volcanic cones and lava flows. Working float back to the host body is the standard way to chase a fresh occurrence.

What is scoria used for?+

Scoria is used in landscaping, road construction, filtration media, industrial aggregate.

Find scoria on the map

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