Alpersite is a rare magnesium-dominant sulfate mineral that typically forms as efflorescent crusts or fibrous aggregates in mine environments. It is most commonly found as a secondary mineral resulting from the oxidation of sulfide ores, particularly in sites affected by acid mine drainage.
Is this alpersite?
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 alpersite with a known reference. Alpersite 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.
- 4Match the color rangeCompare against the expected color range: blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: efflorescences.
Often confused with
Alpersite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside alpersite
Minerals reported to co-occur with alpersite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MgSO₄·7H₂O
- Mohs hardness
- 2.5
- Density
- 1.820 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Efflorescences
- Cleavage
- Good on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Formed from acid mine waste waters with mineralogically zoned assemblages in sheltered areas at a relative humidity of 65% and T = 4 °C. Dehydrates to cuprian pentahydrate
Where rockhounds find alpersite
Classic worldwide localities
- Big Mike mine, on the south side of Panther Canyon, on the west flank of the north end of the Tobin Range, Pershing County, north-central Nevada, USA
Field-hunting tip
Where it forms: Formed from acid mine waste waters with mineralogically zoned assemblages in sheltered areas at a relative humidity of 65% and T = 4 °C. Dehydrates to cuprian pentahydrate. If you start seeing pickeringite, alunogen, epsomite 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 alpersite?+
Where is alpersite found?+
Is alpersite safe to handle?+
What rocks look like alpersite?+
What minerals are found with alpersite?+
What kind of rock does alpersite form in?+
What is alpersite used for?+
Find alpersite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
