Slate is a fine-grained, foliated metamorphic rock that is created by the low-grade metamorphism of shale or mudstone. It is easily identified by its characteristic slaty cleavage, which allows the rock to be split into thin, flat, and durable sheets.

Hardness

2.5-4

Mohs

Luster

Dull

Streak

White

Transparency

Opaque

metamorphiccommon

Slate

Hardness: 2.5-4
Luster: Dull
Streak: White
Transparency: Opaque

Is this slate?

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 slate with a known reference. Slate sits at Mohs 2.5-4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Slate leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Slate typically shows a dull luster.
4
Match the color range
Compare against the expected color range: gray, black, green, red, purple, brown.
5
Look at form & habit
Typical habit: foliated.

Often confused with

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

How to tell apart: Luster reads dull on Slate and silky on Phyllite.

How to tell apart: Luster reads dull on Slate and pearly on Schist.

Compare →

Often found alongside slate

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

All properties

Mohs hardness: 2.5-4
Density: 2.7-2.9 g/cm³
Colors: Gray Black Green Red Purple Brown
Streak: White
Luster: Dull
Transparency: Opaque
Crystal habit: Foliated
Cleavage: Perfect Slaty Cleavage
Rarity: Common
Uses: Construction, Roofing, Flooring, Decorative
Host rock: Low-grade Regional Metamorphism of Shale or Mudstone
Typical price: low, depending on size and intended use

Where rockhounds find slate

Classic worldwide localities

Wales
Pennsylvania, USA
France
Germany
Spain

Field-hunting tip

Look in low-grade regional metamorphism of shale or mudstone country — that is the host setting where slate typically forms. If you start seeing quartz, muscovite, chlorite in float, you are in the right ground. Field specimens usually show a foliated habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify slate?+

Mohs hardness is 2.5-4. It typically shows a dull luster. The streak is white. Common colors include gray, black, green, red.

Where is slate found?+

Notable localities include Wales; Pennsylvania, USA; France; Germany; Spain.

How much is slate worth?+

Typical asking prices fall in the range of low, depending on size and intended use. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like slate?+

Slate is most often confused with Shale, Phyllite, Schist. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with slate?+

Slate commonly co-occurs with Quartz, Muscovite, Chlorite, Hematite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does slate form in?+

Slate typically forms in low-grade regional metamorphism of shale or mudstone. Working float back to the host body is the standard way to chase a fresh occurrence.

What is slate used for?+

Slate is used in construction, roofing, flooring, decorative.

Find slate on the map

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