Richterite is a member of the sodic-calcic amphibole group, typically appearing as elongated, prismatic or fibrous crystals. It is most frequently found in metamorphosed limestone deposits or alkaline rocks, often exhibiting distinct brown or yellow hues.

Hardness

5-6

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent to translucent

mineraluncommonAmphibole Supergroup family

Richterite

Hardness: 5-6
Luster: Vitreous
Streak: White
Transparency: Transparent to translucent

Is this 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 richterite with a known reference. 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, blue, brown red, gray violet, yellow.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular.

Often confused with

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

How to tell apart: Streak differs, so Richterite leaves white, Hornblende leaves grayish-white.

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Often found alongside richterite

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

All properties

Chemical formula: Na(NaCa)Mg₅Si₈O₂₂(OH)₂
Mohs hardness: 5-6
Density: 2.97-3.45 g/cm³
Colors: Brown Blue Brown redGray violetYellow
Streak: White
Luster: Vitreous
Transparency: Transparent to translucent
Crystal system: Monoclinic
Crystal habit: Tabular
Cleavage: Perfect on {110}, intersecting at ~56° and ~124°; partings on {100}, {001}
Rarity: Uncommon
Uses: Collector
Host rock: Commonly in contact metamorphosed limestones; in alkalic igneous rocks and carbonatites

Where rockhounds find richterite

Classic worldwide localities

Iron Hill, Gunnison Co., Colorado and the Leucite Hills, Sweetwater Co., Wyoming, USA
Långban and Pajsberg, Värmland, Sweden
Praborna mine, near St. Marcel, Val d'Aosta, Italy
Kangerdlugssuaq Fjord, Greenland
Murun massif, southwest of Olekminsk, Yakutia, Russia
Gooderham, Wilberforce, Canada

Field-hunting tip

Where it forms: Commonly in contact metamorphosed limestones; in alkalic igneous rocks and carbonatites. If you start seeing leucite, diopside, forsterite in float, you are in the right ground. Typical habit: tabular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify richterite?+

Mohs hardness is 5-6. Luster: vitreous. The streak is white. Common colors include brown, blue, brown red, gray violet.

Where is richterite found?+

Notable localities include Iron Hill, Gunnison Co., Colorado and the Leucite Hills, Sweetwater Co., Wyoming, USA; Långban and Pajsberg, Värmland, Sweden; Praborna mine, near St. Marcel, Val d'Aosta, Italy; Kangerdlugssuaq Fjord, Greenland; Murun massif, southwest of Olekminsk, Yakutia, Russia.

What rocks look like richterite?+

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

What minerals are found with richterite?+

Richterite commonly co-occurs with Leucite, Diopside, Forsterite, Calcite, Apatite, Natrolite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does richterite form in?+

Where it forms: Commonly in contact metamorphosed limestones; in alkalic igneous rocks and carbonatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is richterite used for?+

Richterite is used in collector.

Find richterite on the map

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