Rectorite is a rare regular mixed-layer clay mineral composed of alternating layers of mica and smectite. It typically occurs as soft, pearly, micaceous masses or coatings and is most famously associated with hydrothermal environments and altered igneous rocks.

Hardness

2-3

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineraluncommonSmectite Group family

Rectorite

Hardness: 2-3
Luster: Pearly
Streak: White
Transparency: Translucent

Is this rectorite?

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 rectorite with a known reference. Rectorite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Rectorite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Rectorite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: white, gray, yellowish, brownish.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: platy, micaceous, earthy, massive.

Often confused with

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

How to tell apart: Luster reads pearly on Rectorite and dull on Montmorillonite.

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Often found alongside rectorite

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

All properties

Chemical formula: NaAl₄(Si₇Al)O₂₀(OH)₄·2H₂O
Mohs hardness: 2-3
Density: 2.1-2.3 g/cm³
Colors: White Gray Yellowish Brownish
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Platy, Micaceous, Earthy, Massive
Cleavage: Perfect Basal
Rarity: Uncommon
Uses: Collector, Industrial
Host rock: Hydrothermal Veins, Metamorphosed Shales
Typical price: $10-60 for specimen pieces

Where rockhounds find rectorite

Classic worldwide localities

Magnet Cove, Arkansas, USA
Dagestan, Russia
Fuka, Japan

Field-hunting tip

Look in hydrothermal veins, metamorphosed shales country — that is the host setting where rectorite typically forms. If you start seeing quartz, calcite, dolomite in float, you are in the right ground. Field specimens usually show a platy, micaceous, earthy, massive habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify rectorite?+

Mohs hardness is 2-3. It typically shows a pearly luster. The streak is white. Common colors include white, gray, yellowish, brownish.

Where is rectorite found?+

Notable localities include Magnet Cove, Arkansas, USA; Dagestan, Russia; Fuka, Japan.

How much is rectorite worth?+

Typical asking prices fall in the range of $10-60 for specimen pieces. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like rectorite?+

Rectorite is most often confused with Muscovite, Illite, Montmorillonite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with rectorite?+

Rectorite commonly co-occurs with Quartz, Calcite, Dolomite, Pyrite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does rectorite form in?+

Rectorite typically forms in hydrothermal veins, metamorphosed shales. Working float back to the host body is the standard way to chase a fresh occurrence.

What is rectorite used for?+

Rectorite is used in collector, industrial.

Find rectorite on the map

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