Proto-ferro-anthophyllite is a rare member of the amphibole group found in high-grade metamorphic environments. It typically occurs as prismatic or fibrous crystals and is often chemically related to anthophyllite and grunerite, requiring laboratory analysis for definitive identification.

Hardness

5-6

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareAmphibole Supergroup family

Proto-ferro-anthophyllite

Hardness: 5-6
Luster: Vitreous
Streak: White
Transparency: Translucent

No image

Is this proto-ferro-anthophyllite?

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 proto-ferro-anthophyllite with a known reference. Proto-ferro-anthophyllite 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. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: brown, greenish-brown, dark gray.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: fibrous, prismatic, or massive aggregates.

Often confused with

Proto-ferro-anthophyllite vs. its common look-alikes, and how to tell them apart in the field.

How to tell apart: Streak differs, so Proto-ferro-anthophyllite leaves white, Cummingtonite leaves grayish white.

How to tell apart: Streak differs, so Proto-ferro-anthophyllite leaves white, Grunerite leaves colorless.

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Often found alongside proto-ferro-anthophyllite

Minerals reported to co-occur with proto-ferro-anthophyllite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Fe₇Si₈O₂₂(OH)₂
Mohs hardness: 5-6
Density: 3.3-3.5 g/cm³
Colors: Brown Greenish-brown Dark gray
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Fibrous, prismatic, or massive aggregates
Cleavage: Perfect in two directions
Rarity: Rare
Uses: Collector
Host rock: metamorphic rocks

Where rockhounds find proto-ferro-anthophyllite

Classic worldwide localities

Norway
Sweden
Finland

Field-hunting tip

Where it forms: metamorphic rocks. If you start seeing quartz, garnet, staurolite in float, you are in the right ground. Typical habit: fibrous, prismatic, or massive aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify proto-ferro-anthophyllite?+

Mohs hardness is 5-6. Luster: vitreous. The streak is white. Common colors include brown, greenish-brown, dark gray.

Where is proto-ferro-anthophyllite found?+

Notable localities include Norway; Sweden; Finland.

Is proto-ferro-anthophyllite safe to handle?+

Asbestiform varieties may pose inhalation risks; handle with care to avoid generating dust.

What rocks look like proto-ferro-anthophyllite?+

Proto-ferro-anthophyllite is most often confused with Anthophyllite, Cummingtonite, Grunerite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with proto-ferro-anthophyllite?+

Proto-ferro-anthophyllite commonly co-occurs with quartz, garnet, staurolite, biotite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does proto-ferro-anthophyllite form in?+

Where it forms: metamorphic rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is proto-ferro-anthophyllite used for?+

Proto-ferro-anthophyllite is used in collector.

Find proto-ferro-anthophyllite on the map

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