Sanderite is a rare magnesium sulfate mineral that typically forms as a secondary product in salt mines. Collectors should look for delicate white fibrous or needle-like crusts on other evaporite minerals, though it is often prone to dehydration and requires careful storage.
Is this sanderite?
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 sanderite with a known reference. Sanderite 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: vitreous.
- 4Match the color rangeCompare against the expected color range: white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: efflorescences.
Often confused with
Sanderite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside sanderite
Minerals reported to co-occur with sanderite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MgSO₄·2H₂O
- Mohs hardness
- 2
- Density
- 2.37 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Efflorescences
- Cleavage
- Perfect in one direction
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Structure analyzed from synthetic material
Where rockhounds find sanderite
Classic worldwide localities
- Efflorescences on kieserite at the Hansa I shaft, Empelde, and the Niedersachsen shaft, near Wathlingen, Austria (type locality)
Field-hunting tip
Where it forms: Structure analyzed from synthetic material. If you start seeing halite, kieserite, carnallite in float, you are in the right ground. Typical habit: efflorescences. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify sanderite?+
Where is sanderite found?+
What rocks look like sanderite?+
What minerals are found with sanderite?+
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Find sanderite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
