Pumpellyite-(Al) is a sorosilicate mineral typically found in low-grade metamorphic rocks, particularly altered basalts. It is easily identified by its characteristic green color and often appears as fine-grained, radiating, or fibrous aggregates in vesicles and fractures.

Hardness

5.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineraluncommonPumpellyite Group family

Pumpellyite-(Al)

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

Is this pumpellyite-(al)?

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-(al) with a known reference. Pumpellyite-(Al) 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-(Al) leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Pumpellyite-(Al) typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: green, bluish-green, brownish-green, yellowish-green.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: fibrous, radiating, platy aggregates, massive.

Often confused with

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

Often found alongside pumpellyite-(al)

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

All properties

Chemical formula: Ca₂Al₂Mg(Si₂O₇)(SiO₄)(OH)₂·H₂O
Mohs hardness: 5.5
Density: 3.18-3.23 g/cm³
Colors: Green Bluish-green Brownish-green Yellowish-green
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Fibrous, Radiating, Platy Aggregates, Massive
Cleavage: Good On {001}
Rarity: Uncommon
Uses: Collector
Host rock: Metamorphic Basalt, Low-grade Metamorphic Rocks
Typical price: $10-50 per specimen depending on size and crystal clarity.

Where rockhounds find pumpellyite-(al)

Classic worldwide localities

Keweenaw Peninsula, Michigan, USA
Hokkaido, Japan
New Caledonia
Western Alps, Italy

Field-hunting tip

Look in metamorphic basalt, low-grade metamorphic rocks country — that is the host setting where pumpellyite-(al) typically forms. If you start seeing chlorite, quartz, calcite in float, you are in the right ground. Field specimens usually show a fibrous, radiating, platy aggregates, massive habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify pumpellyite-(al)?+

Mohs hardness is 5.5. It typically shows a vitreous luster. The streak is white. Common colors include green, bluish-green, brownish-green, yellowish-green.

Where is pumpellyite-(al) found?+

Notable localities include Keweenaw Peninsula, Michigan, USA; Hokkaido, Japan; New Caledonia; Western Alps, Italy.

How much is pumpellyite-(al) worth?+

Typical asking prices fall in the range of $10-50 per specimen depending on size and crystal clarity.. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like pumpellyite-(al)?+

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

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

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

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

Pumpellyite-(Al) typically forms in metamorphic basalt, low-grade metamorphic rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is pumpellyite-(al) used for?+

Pumpellyite-(Al) is used in collector.

Find pumpellyite-(al) on the map

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