Cummingtonite is a monoclinic amphibole that typically forms fibrous or columnar masses in metamorphic environments. It is most easily identified by its characteristic brownish-grey color and its tendency to occur in radiating or bladed habit. It is found in metamorphosed iron-rich deposits and regional metamorphic rocks.

Hardness

5-6

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineraluncommonAmphibole Group family

Cummingtonite

Hardness: 5-6
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this cummingtonite?

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 cummingtonite with a known reference. Cummingtonite 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. Cummingtonite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Cummingtonite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: brown, gray, greenish-gray, tan.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: fibrous, columnar, lamellar, or radiating aggregates.

Often confused with

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

How to tell apart: Luster reads vitreous on Cummingtonite and vitreous to silky on Actinolite.

Compare →

Often found alongside cummingtonite

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

All properties

Chemical formula: □Mg₂(Mg₅)Si₈O₂₂(OH)₂
Mohs hardness: 5-6
Density: 3.1-3.5 g/cm³
Colors: Brown Gray Greenish-gray Tan
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Fibrous, Columnar, Lamellar, Or Radiating Aggregates
Cleavage: Perfect in Two Directions At 56 and 124 Degrees
Rarity: Uncommon
Uses: Collector, Scientific Research
Host rock: Metamorphosed Iron-rich Rocks, Amphibolites, And Contact Metamorphic Zones
Typical price: $10-60 thumbnail, $50-200 cabinet specimen

Where rockhounds find cummingtonite

1 mapped spots

Classic worldwide localities

Cummington, Massachusetts, USA
Bod Bodenmais, Bavaria, Germany
Franklin, New Jersey, USA
Dalnegorsk, Russia

Field-hunting tip

Look in metamorphosed iron-rich rocks, amphibolites, and contact metamorphic zones country — that is the host setting where cummingtonite typically forms. If you start seeing garnet, hornblende, magnetite in float, you are in the right ground. Field specimens usually show a fibrous, columnar, lamellar, or radiating aggregates habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Wisconsin — start trip planning there.

Browse 1 U.S. spots for cummingtonite →

Common questions

How do you identify cummingtonite?+

Mohs hardness is 5-6. It typically shows a vitreous luster. The streak is white. Common colors include brown, gray, greenish-gray, tan.

Where is cummingtonite found?+

Notable localities include Cummington, Massachusetts, USA; Bod Bodenmais, Bavaria, Germany; Franklin, New Jersey, USA; Dalnegorsk, Russia.

Can I find cummingtonite in the United States?+

RockHoundR maps 1 cummingtonite rockhounding spots across 1 U.S. states — the top states are Wisconsin.

How much is cummingtonite worth?+

Typical asking prices fall in the range of $10-60 thumbnail, $50-200 cabinet specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like cummingtonite?+

Cummingtonite is most often confused with Anthophyllite, Tremolite, Actinolite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with cummingtonite?+

Cummingtonite commonly co-occurs with Garnet, Hornblende, Magnetite, Quartz, Staurolite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does cummingtonite form in?+

Cummingtonite typically forms in metamorphosed iron-rich rocks, amphibolites, and contact metamorphic zones. Working float back to the host body is the standard way to chase a fresh occurrence.

What is cummingtonite used for?+

Cummingtonite is used in collector, scientific research.

Find cummingtonite on the map

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