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.
Is this loughlinite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch loughlinite with a known reference. Loughlinite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: silky.
- 4Match the color rangeCompare against the expected color range: pearl white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: massive.
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
- 2.165 g/cm³
- Colors
- Streak
- White
- Luster
- Silky
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- As replacements in dolomitic medium- to low-grade oil shale of the Green River Formation (Sweetwater Co., Wyoming, USA)
Where rockhounds find loughlinite
Classic worldwide localities
- Core from the John Hay, Jr. Well No. 1 and the Union Pacific Well No. 4, and in the shaft of the Westvaco trona mine, Sweetwater Co., Wyoming, USA
Field-hunting tip
Where it forms: As replacements in dolomitic medium- to low-grade oil shale of the Green River Formation (Sweetwater Co., Wyoming, USA). If you start seeing shortite, northupite, searlesite in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify loughlinite?+
Where is loughlinite found?+
What rocks look like loughlinite?+
What minerals are found with loughlinite?+
What kind of rock does loughlinite form in?+
What is loughlinite used for?+
Find loughlinite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
