Loughlinite is a rare fibrous sodium-magnesium silicate belonging to the sepiolite group. It is primarily found as crusts or fibrous masses in alkaline evaporitic lake deposits like the Green River Formation. Because of its structural similarity to sepiolite, it often requires X-ray diffraction for definitive identification.

Hardness

Mohs

Luster

Dull

Streak

White

Transparency

Opaque

mineralrareSepiolite Group family

Loughlinite

Hardness: 2
Luster: Dull
Streak: White
Transparency: Opaque

Is this loughlinite?

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 loughlinite with a known reference. Loughlinite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Loughlinite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Loughlinite typically shows a dull luster.
4
Match the color range
Compare against the expected color range: white, gray.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: fibrous.

Often confused with

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

Often found alongside loughlinite

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

All properties

Chemical formula: Na₂Mg₃Si₆O₁₆·8H₂O
Mohs hardness: 2
Density: 2.12 g/cm³
Colors: White Gray
Streak: White
Luster: Dull
Transparency: Opaque
Crystal system: Orthorhombic
Crystal habit: Fibrous
Cleavage: None
Rarity: Rare
Uses: Collector, Scientific Research
Host rock: Evaporitic Lacustrine Sedimentary Rocks
Typical price: $20-150 for small specimens

Where rockhounds find loughlinite

Classic worldwide localities

Green River Formation, Wyoming, USA
Utah, USA

Field-hunting tip

Look in evaporitic lacustrine sedimentary rocks country — that is the host setting where loughlinite typically forms. If you start seeing shortite, searlesite, analcime in float, you are in the right ground. Field specimens usually show a fibrous habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify loughlinite?+

Mohs hardness is 2. It typically shows a dull luster. The streak is white. Common colors include white, gray.

Where is loughlinite found?+

Notable localities include Green River Formation, Wyoming, USA; Utah, USA.

How much is loughlinite worth?+

Typical asking prices fall in the range of $20-150 for small specimens. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like loughlinite?+

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

What minerals are found with loughlinite?+

Loughlinite commonly co-occurs with Shortite, Searlesite, Analcime, Dolomite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does loughlinite form in?+

Loughlinite typically forms in evaporitic lacustrine sedimentary rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is loughlinite used for?+

Loughlinite is used in collector, scientific research.

Find loughlinite on the map

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