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.
Is this pumpellyite-(al)?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry 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.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: colorless.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous.
Often confused with
Pumpellyite-(Al) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Pumpellyite-(Al) leaves colorless, Epidote leaves grayish white.
How to tell apart: Streak differs, so Pumpellyite-(Al) leaves colorless, Prehnite leaves white.
How to tell apart: Clinozoisite is the harder of the two (Mohs 6.5 vs. 5.5); streak differs, so Pumpellyite-(Al) leaves colorless, Clinozoisite leaves grayish white.
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
- Ca₂Al₃(SiO₄)(Si₂O₇)(OH,O)₂·H₂O
- Mohs hardness
- 5.5
- Density
- 3.41 g/cm³
- Colors
- Streak
- Colorless
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous
- Cleavage
- Perfect on {100}
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- In veins cutting retrograde metamorphosed sedimentary rocks
Where rockhounds find pumpellyite-(al)
Classic worldwide localities
- Carrière de la Flèche quarry, near Bertrix, Ardennes, Belgium (type locality)
Field-hunting tip
Where it forms: In veins cutting retrograde metamorphosed sedimentary rocks. If you start seeing calcite, k-feldspar, chlorite in float, you are in the right ground. Typical habit: fibrous. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify pumpellyite-(al)?+
Where is pumpellyite-(al) found?+
What rocks look like pumpellyite-(al)?+
What minerals are found with pumpellyite-(al)?+
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What is pumpellyite-(al) used for?+
Find pumpellyite-(al) on the map
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