Apjohnite is a secondary sulfate mineral that typically forms as delicate, fibrous efflorescences in mine workings and volcanic environments. Because it is highly soluble in water and dehydration-prone, collectors should store specimens in airtight containers to prevent them from crumbling into powder.
Is this apjohnite?
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 apjohnite with a known reference. Apjohnite sits at Mohs 1.5-2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Apjohnite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Apjohnite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, pale yellow, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, acicular, efflorescent, or crusts.
Often confused with
Apjohnite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside apjohnite
Minerals reported to co-occur with apjohnite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MnAl₂(SO₄)₄·22H₂O
- Mohs hardness
- 1.5-2
- Density
- 1.7-1.8 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, Acicular, Efflorescent, Or Crusts
- Cleavage
- Distinct On {110}
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Oxidized Ore Deposits and Coal Mine Workings
- Typical price
- $10-60 for small specimens
Where rockhounds find apjohnite
Classic worldwide localities
- South Africa
- United States
- Czech Republic
- Germany
Field-hunting tip
Look in oxidized ore deposits and coal mine workings country, the host setting where apjohnite typically forms. If you start seeing gypsum, jarosite, melanterite in float, you are in the right ground. Field specimens usually show a fibrous, acicular, efflorescent, or crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify apjohnite?+
Where is apjohnite found?+
How much is apjohnite worth?+
What rocks look like apjohnite?+
What minerals are found with apjohnite?+
What kind of rock does apjohnite form in?+
What is apjohnite used for?+
Find apjohnite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
