Diorite is a coarse-grained plutonic rock primarily composed of plagioclase feldspar and dark ferromagnesian minerals like hornblende or biotite. It lacks significant quartz, which distinguishes it visually from granite by its darker, salt-and-pepper appearance. Historically prized for its hardness, it is often found in large intrusive igneous masses.

Hardness

6-7

Mohs

Luster

Vitreous

Streak

White

Transparency

Opaque

igneouscommon

Diorite

Hardness: 6-7
Luster: Vitreous
Streak: White
Transparency: Opaque

Is this diorite?

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 diorite with a known reference. Diorite sits at Mohs 6-7 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Diorite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Diorite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: gray, black, white.
5
Look at form & habit
Typical habit: granular.

Often confused with

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

How to tell apart: Streak differs — Diorite leaves white, Gabbro leaves none.

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Often found alongside diorite

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

All properties

Mohs hardness: 6-7
Density: 2.8-3.0 g/cm³
Colors: Gray Black White
Streak: White
Luster: Vitreous
Transparency: Opaque
Crystal habit: Granular
Cleavage: None
Rarity: Common
Uses: Construction, Sculpture, Decorative
Host rock: Plutonic Igneous Environments
Typical price: $1-10 per sample

Where rockhounds find diorite

Classic worldwide localities

Scotland
Germany
Finland
Sweden
United States

Field-hunting tip

Look in plutonic igneous environments country — that is the host setting where diorite typically forms. If you start seeing plagioclase, biotite, hornblende in float, you are in the right ground. Field specimens usually show a granular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify diorite?+

Mohs hardness is 6-7. It typically shows a vitreous luster. The streak is white. Common colors include gray, black, white.

Where is diorite found?+

Notable localities include Scotland; Germany; Finland; Sweden; United States.

How much is diorite worth?+

Typical asking prices fall in the range of $1-10 per sample. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like diorite?+

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

What minerals are found with diorite?+

Diorite commonly co-occurs with Plagioclase, Biotite, Hornblende, Pyroxene. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does diorite form in?+

Diorite typically forms in plutonic igneous environments. Working float back to the host body is the standard way to chase a fresh occurrence.

What is diorite used for?+

Diorite is used in construction, sculpture, decorative.

Find diorite on the map

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