Chesterite is a very rare polysomatic mineral first discovered in the ultramafic rocks of Vermont. It is typically found as lamellar or fibrous masses and is often intergrown with anthophyllite, making visual identification difficult without laboratory analysis.

Hardness

5-6

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareAmphibole Supergroup family

Chesterite

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

Is this chesterite?

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 chesterite with a known reference. Chesterite 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. Chesterite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Chesterite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: dark brown, brownish-black.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: fibrous, lamellar aggregates.

Often confused with

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

How to tell apart: Chesterite is noticeably harder (Mohs 5-6 vs. 1); luster reads vitreous on Chesterite and pearly on Talc.

Often found alongside chesterite

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

All properties

Chemical formula: (Mg,Fe)₁₇Si₁₆O₄₄(OH)₂
Mohs hardness: 5-6
Density: 3.1-3.2 g/cm³
Colors: Dark Brown Brownish-black
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Fibrous, Lamellar Aggregates
Cleavage: Perfect
Rarity: Rare
Uses: Collector
Host rock: Metamorphic Rocks, Specifically Ultramafic Schists
Typical price: $20-150 per specimen depending on size and quality

Where rockhounds find chesterite

Classic worldwide localities

Chester, Vermont, USA
Tillotson Peak, Vermont, USA

Field-hunting tip

Look in metamorphic rocks, specifically ultramafic schists country — that is the host setting where chesterite typically forms. If you start seeing anthophyllite, talc, kyanite in float, you are in the right ground. Field specimens usually show a fibrous, lamellar aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify chesterite?+

Mohs hardness is 5-6. It typically shows a vitreous luster. The streak is white. Common colors include dark brown, brownish-black.

Where is chesterite found?+

Notable localities include Chester, Vermont, USA; Tillotson Peak, Vermont, USA.

How much is chesterite worth?+

Typical asking prices fall in the range of $20-150 per specimen depending on size and quality. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like chesterite?+

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

What minerals are found with chesterite?+

Chesterite commonly co-occurs with Anthophyllite, Talc, Kyanite, Garnet. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does chesterite form in?+

Chesterite typically forms in metamorphic rocks, specifically ultramafic schists. Working float back to the host body is the standard way to chase a fresh occurrence.

What is chesterite used for?+

Chesterite is used in collector.

Find chesterite on the map

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