Ferro-richterite is a rare member of the amphibole supergroup characterized by high iron content and an elongated prismatic habit. Collectors prize this mineral for its distinct, often dark-toned, elongate crystals typically found in alkaline environments and contact metamorphic zones.

Hardness

5-6

Mohs

Luster

Vitreous

Streak

White

Transparency

Semitransparent

mineralrareAmphibole Group family

Ferro-richterite

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

Is this ferro-richterite?

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 ferro-richterite with a known reference. Ferro-richterite 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, green.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic crystals, fibrous.

Often confused with

Ferro-richterite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Arfvedsonite

Mohs 5-6

How to tell apart: Streak differs, so Ferro-richterite leaves white, Arfvedsonite leaves deep bluish gray, gray-green.

Often found alongside ferro-richterite

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

All properties

Chemical formula: Na(NaCa)Fe²⁺₅Si₈O₂₂(OH)₂
Mohs hardness: 5-6
Density: 3.46 g/cm³
Colors: Brown Green
Streak: White
Luster: Vitreous
Transparency: Semitransparent
Crystal system: Monoclinic
Crystal habit: Prismatic crystals, fibrous
Cleavage: Perfect on {110}, intersecting at ~56° and ~124°; partings on {100}, {001}
Rarity: Rare
Uses: Collector, Scientific research
Host rock: A rare accessory mineral in sodium-rich syenites and their volcanic equivalents; replacing ferromagnesian minerals in granite

Where rockhounds find ferro-richterite

Classic worldwide localities

Kangerdlugssuaq Fjord, Greenland
Tibchi ring complex, Nigeria

Field-hunting tip

Where it forms: A rare accessory mineral in sodium-rich syenites and their volcanic equivalents; replacing ferromagnesian minerals in granite. If you start seeing feldspar, pyroxenes, zircon in float, you are in the right ground. Typical habit: prismatic crystals, fibrous. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify ferro-richterite?+

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

Where is ferro-richterite found?+

Notable localities include Kangerdlugssuaq Fjord, Greenland; Tibchi ring complex, Nigeria.

What rocks look like ferro-richterite?+

Ferro-richterite is most often confused with Arfvedsonite, Richterite, Tremolite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with ferro-richterite?+

Ferro-richterite commonly co-occurs with Feldspar, Pyroxenes, Zircon, Fayalite, Ferro-actinolite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does ferro-richterite form in?+

Where it forms: A rare accessory mineral in sodium-rich syenites and their volcanic equivalents; replacing ferromagnesian minerals in granite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is ferro-richterite used for?+

Ferro-richterite is used in collector, scientific research.

Find ferro-richterite on the map

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