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.

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, 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.