Lansfordite is a rare, hydrated magnesium carbonate that is highly unstable when removed from its native environment. It typically forms as white, prismatic crystals or encrustations and will rapidly dehydrate into nesquehonite upon exposure to air. Collectors usually keep these specimens in sealed containers to prevent them from turning into a white, powdery mass.
Is this lansfordite?
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 lansfordite with a known reference. Lansfordite sits at Mohs 2.5, 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: vitreous if fresh.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic to acicular crystals, often as crusts or globular aggregates.
Often confused with
Lansfordite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside lansfordite
Minerals reported to co-occur with lansfordite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MgCO₃·5H₂O
- Mohs hardness
- 2.5
- Density
- 1.692 g/cm³
- Streak
- White
- Luster
- Vitreous if fresh
- Transparency
- Transparent to translucent, becoming opaque on exposure
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic to acicular crystals, often as crusts or globular aggregates
- Cleavage
- {001}, perfect; {100}, less perfect
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- Stalactites pendant from the shale roof of an anthracite coal mine (Nesquehoning, Pennsylvania, USA); in a hydromagnesite deposit (Atlin, Canada); a weathering product of an ultramafic body (Sør-Trøndelag, Norway)
Where rockhounds find lansfordite
Classic worldwide localities
- Nesquehoning, near Lansford, Carbon Co., Pennsylvania, USA
- Robinson Gulch pegmatite, Jefferson Co., Colorado, USA
- Atlin, British Columbia, Canada
- Cogne, Val d’Aosta, Piedmont, Italy
- Feragen ultramafic body, Sør-Trøndelag, Norway
Field-hunting tip
Where it forms: Stalactites pendant from the shale roof of an anthracite coal mine (Nesquehoning, Pennsylvania, USA); in a hydromagnesite deposit (Atlin, Canada); a weathering product of an ultramafic body (Sør-Trøndelag, Norway). If you start seeing nesquehonite, hydromagnesite, dypingite in float, you are in the right ground. Typical habit: prismatic to acicular crystals, often as crusts or globular aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify lansfordite?+
Where is lansfordite found?+
What rocks look like lansfordite?+
What minerals are found with lansfordite?+
What kind of rock does lansfordite form in?+
What is lansfordite used for?+
Find lansfordite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
