Clinoferrosilite is a rare monoclinic pyroxene found primarily in high-grade metamorphic iron formations. It is difficult to distinguish from orthopyroxene without laboratory analysis and is most prized by advanced mineral collectors specializing in silicate species.

Hardness

5-6

Mohs

Luster

Vitreous

Streak

White

Transparency

Semitransparent

mineralrarePyroxene Group family

Clinoferrosilite

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

Is this clinoferrosilite?

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 clinoferrosilite with a known reference. Clinoferrosilite 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, colorless, green.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic crystals, massive.

Often confused with

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

Often found alongside clinoferrosilite

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

All properties

Chemical formula: Fe₂Si₂O₆
Mohs hardness: 5-6
Density: 4.068 g/cm³
Colors: Brown Colorless Green
Streak: White
Luster: Vitreous
Transparency: Semitransparent
Crystal system: Monoclinic
Crystal habit: Prismatic crystals, massive
Cleavage: Good on {110}, (110) ^ (110) ~87° (by analogy to ferrosilite)
Rarity: Rare
Uses: Collector
Host rock: As acicular crystals in lithophysae in obsidian (Lake Naivasha, Kenya)

Where rockhounds find clinoferrosilite

Classic worldwide localities

Coso Mountains, Inyo Co., California, USA
Obsidian Cliffs, Yellowstone National Park, Wyoming, USA
Lake Naivasha, Rift Valley, Kenya
Hrafntinnuhryggur, Iceland

Field-hunting tip

Where it forms: As acicular crystals in lithophysae in obsidian (Lake Naivasha, Kenya). If you start seeing anorthoclase, magnetite, cristobalite in float, you are in the right ground. Typical habit: prismatic crystals, massive. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify clinoferrosilite?+

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

Where is clinoferrosilite found?+

Notable localities include Coso Mountains, Inyo Co., California, USA; Obsidian Cliffs, Yellowstone National Park, Wyoming, USA; Lake Naivasha, Rift Valley, Kenya; Hrafntinnuhryggur, Iceland.

What rocks look like clinoferrosilite?+

Clinoferrosilite is most often confused with Hedenbergite, Fayalite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with clinoferrosilite?+

Clinoferrosilite commonly co-occurs with Anorthoclase, Magnetite, Cristobalite, Fayalite, Biotite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does clinoferrosilite form in?+

Where it forms: As acicular crystals in lithophysae in obsidian (Lake Naivasha, Kenya). Working float back to the host body is the standard way to chase a fresh occurrence.

What is clinoferrosilite used for?+

Clinoferrosilite is used in collector.

Find clinoferrosilite on the map

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