Mountkeithite is a rare layered double hydroxide mineral typically found in serpentinized nickel-rich ultramafic environments. Collectors generally find it as small, white to pale yellow scaly or platy aggregates forming thin crusts or films on matrix material.
Is this mountkeithite?
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 mountkeithite with a known reference. Mountkeithite 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: pearly.
- 4Match the color rangeCompare against the expected color range: white, light pink.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: flakes, granular, rosette.
Often confused with
Mountkeithite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Mountkeithite leaves white, Stichtite leaves very pale lilac to white; luster reads pearly on Mountkeithite and waxy to resinous, somewhat pearly on Stichtite.
How to tell apart: Luster reads pearly on Mountkeithite and satiny to greasy or waxy on Hydrotalcite.
Often found alongside mountkeithite
Minerals reported to co-occur with mountkeithite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Mg₁-xFex)(SO₄)x/2(OH)₂·nH₂O (x < 0.5, n > 3x/2)
- Mohs hardness
- 2
- Density
- 2.12 g/cm³
- Colors
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Hexagonal
- Crystal habit
- Flakes, granular, rosette
- Cleavage
- Perfect on {0001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Rare in a vein in serpentinite in a disseminated nickel sulfide deposit, formed by low-temperature alteration of stichtite by sulfate-rich solutions
Where rockhounds find mountkeithite
Classic worldwide localities
- Mount Keith nickel deposit, 400 km north-northwest of Kalgoorlie, Western Australia
Field-hunting tip
Where it forms: Rare in a vein in serpentinite in a disseminated nickel sulfide deposit, formed by low-temperature alteration of stichtite by sulfate-rich solutions. If you start seeing stichtite, morenosite, hexahydrite in float, you are in the right ground. Typical habit: flakes, granular, rosette. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify mountkeithite?+
Where is mountkeithite found?+
What rocks look like mountkeithite?+
What minerals are found with mountkeithite?+
What kind of rock does mountkeithite form in?+
What is mountkeithite used for?+
Find mountkeithite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
