Pumpellyite-(Mg) is a sorosilicate mineral frequently found as a secondary mineral in altered igneous rocks. It is most recognized for its distinct radiating or fibrous habit in shades of green and blue-green, often forming within veins or amygdules.

Hardness

5.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineraluncommonPumpellyite Group family

Pumpellyite-(Mg)

Hardness: 5.5
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this pumpellyite-(mg)?

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 pumpellyite-(mg) with a known reference. Pumpellyite-(Mg) sits at Mohs 5.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Pumpellyite-(Mg) leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Pumpellyite-(Mg) typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: green, blue-green, brown, black.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: fibrous, radiating, or acicular crystals; also massive.

Often confused with

Pumpellyite-(Mg) vs. its common look-alikes — and how to tell them apart in the field.

How to tell apart: Lawsonite is the harder of the two (Mohs 8 vs. 5.5).

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Often found alongside pumpellyite-(mg)

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

All properties

Chemical formula: Ca₂MgAl₂(SiO₄)(Si₂O₇)(OH)₂·H₂O
Mohs hardness: 5.5
Density: 3.1-3.2 g/cm³
Colors: Green Blue-green Brown Black
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Fibrous, Radiating, Or Acicular Crystals; Also Massive
Cleavage: Poor
Rarity: Uncommon
Uses: Collector, Scientific Research
Host rock: Low-grade Metamorphic Rocks, Particularly Metabasalt and Glaucophane Schist
Typical price: $10-50 thumbnail

Where rockhounds find pumpellyite-(mg)

Classic worldwide localities

Keweenaw Peninsula, USA
New Caledonia
Val Malenco, Italy
Japan

Field-hunting tip

Look in low-grade metamorphic rocks, particularly metabasalt and glaucophane schist country — that is the host setting where pumpellyite-(mg) typically forms. If you start seeing epidote, prehnite, quartz in float, you are in the right ground. Field specimens usually show a fibrous, radiating, or acicular crystals; also massive habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify pumpellyite-(mg)?+

Mohs hardness is 5.5. It typically shows a vitreous luster. The streak is white. Common colors include green, blue-green, brown, black.

Where is pumpellyite-(mg) found?+

Notable localities include Keweenaw Peninsula, USA; New Caledonia; Val Malenco, Italy; Japan.

How much is pumpellyite-(mg) worth?+

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

What rocks look like pumpellyite-(mg)?+

Pumpellyite-(Mg) is most often confused with Epidote, Prehnite, Lawsonite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with pumpellyite-(mg)?+

Pumpellyite-(Mg) commonly co-occurs with Epidote, Prehnite, Quartz, Calcite, Chlorite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does pumpellyite-(mg) form in?+

Pumpellyite-(Mg) typically forms in low-grade metamorphic rocks, particularly metabasalt and glaucophane schist. Working float back to the host body is the standard way to chase a fresh occurrence.

What is pumpellyite-(mg) used for?+

Pumpellyite-(Mg) is used in collector, scientific research.

Find pumpellyite-(mg) on the map

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