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, 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.