Pumpellyite-(Fe2+) is a characteristic mineral of the prehnite-pumpellyite metamorphic facies, often found as fibrous or radiating green crusts. Collectors usually encounter it as microscopic inclusions or fine-grained mats within altered basaltic rocks, particularly in the Lake Superior copper districts.
Is this pumpellyite-(fe2+)?
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-(fe2+) with a known reference. Pumpellyite-(Fe2+) sits at Mohs 5.5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: green, brownish-green, blackish-green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, acicular, radiating aggregates, or massive.
Often confused with
Pumpellyite-(Fe2+) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Pumpellyite-(Fe2+) leaves white, Epidote leaves grayish white.
How to tell apart: Streak differs, so Pumpellyite-(Fe2+) leaves white, Clinozoisite leaves grayish white.
Often found alongside pumpellyite-(fe2+)
Minerals reported to co-occur with pumpellyite-(fe2+). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Fe²⁺Al₂(Si₂O₇)(SiO₄)(OH)₂·H₂O
- Mohs hardness
- 5.5-6
- Density
- 3.31 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, acicular, radiating aggregates, or massive
- Cleavage
- Poor
- Rarity
- Uncommon
- Uses
- Collector, Scientific research
- Host rock
- In the contact zone around an intrusive
Where rockhounds find pumpellyite-(fe2+)
Classic worldwide localities
- Keweenaw Peninsula, Michigan, USA
- New Caledonia
- Japan
- Italy
- California, USA
Field-hunting tip
Where it forms: In the contact zone around an intrusive. If you start seeing prehnite, babingtonite, clinopyroxene in float, you are in the right ground. Typical habit: fibrous, acicular, radiating aggregates, or massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify pumpellyite-(fe2+)?+
Where is pumpellyite-(fe2+) found?+
What rocks look like pumpellyite-(fe2+)?+
What minerals are found with pumpellyite-(fe2+)?+
What kind of rock does pumpellyite-(fe2+) form in?+
What is pumpellyite-(fe2+) used for?+
Find pumpellyite-(fe2+) on the map
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