Kempite is an extremely rare manganese chloride hydroxide typically found as small, vibrant emerald-green grains or crusts. It is most famous for its occurrence in the manganese-rich deposits of California's Alum Rock Park, where it forms in association with other manganese minerals.
Is this kempite?
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 kempite with a known reference. Kempite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Kempite leaves a pale green streak.
- 3Read the lusterHold the specimen under a strong light. Kempite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: emerald-green, olive-green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: granular, massive, thin crusts.
Often confused with
Kempite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Kempite leaves pale green, Atacamite leaves apple green; luster reads vitreous on Kempite and adamantine to vitreous on Atacamite.
How to tell apart: Lawsonite is the harder of the two (Mohs 8 vs. 3.5); streak differs, so Kempite leaves pale green, Lawsonite leaves white.
Often found alongside kempite
Minerals reported to co-occur with kempite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn₂Cl(OH)₃
- Mohs hardness
- 3.5
- Density
- 3.2 g/cm³
- Colors
- Streak
- Pale Green
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Granular, Massive, Thin Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Manganese Deposits in Chert
- Typical price
- $50-300 per specimen
Where rockhounds find kempite
Classic worldwide localities
- Alum Rock Park, San Jose, California, USA
Field-hunting tip
Look in manganese deposits in chert country, the host setting where kempite typically forms. If you start seeing hausmannite, neotocite, rhodochrosite in float, you are in the right ground. Field specimens usually show a granular, massive, thin crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kempite?+
Where is kempite found?+
How much is kempite worth?+
What rocks look like kempite?+
What minerals are found with kempite?+
What kind of rock does kempite form in?+
What is kempite used for?+
Find kempite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
