Woodallite is a rare hydrated magnesium chromium chloride hydroxide mineral found in serpentinized ultramafic rocks. It typically forms as thin, yellow-to-purple platy crystals or aggregates within chromite-rich environments, specifically known from the Woodall mine in Western Australia.
Is this woodallite?
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 woodallite with a known reference. Woodallite 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. Streak: pale pink to white.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous to waxy.
- 4Match the color rangeCompare against the expected color range: purple, deep magenta.
- 5Look at form & habitCrystal system: trigonal. Typical habit: platy.
Often confused with
Woodallite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Woodallite leaves pale pink to white, Hydrotalcite leaves white; luster reads resinous to waxy on Woodallite and satiny to greasy or waxy on Hydrotalcite.
How to tell apart: Streak differs, so Woodallite leaves pale pink to white, Stichtite leaves very pale lilac to white; luster reads resinous to waxy on Woodallite and waxy to resinous, somewhat pearly on Stichtite.
Often found alongside woodallite
Minerals reported to co-occur with woodallite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mg₆Cr₂(OH)₁₆Cl₂·4H₂O
- Mohs hardness
- 1.5-2
- Density
- 2.062 g/cm³
- Colors
- PurpleDeep magenta
- Streak
- Pale pink to white
- Luster
- Resinous to waxy
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Platy
- Cleavage
- Perfect on {0001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a low-grade, disseminated nickel sulfide deposit in lizardite+brucite-altered dunite formed by hydrothermal alteration of primary magmatic chromite by Cl-rich solutions at temperatures < 320o C
Where rockhounds find woodallite
Classic worldwide localities
- Mount Keith nickel deposit, about 90 km NNE of Leinster, northeastern Goldfields district, Western Australia
Field-hunting tip
Where it forms: In a low-grade, disseminated nickel sulfide deposit in lizardite+brucite-altered dunite formed by hydrothermal alteration of primary magmatic chromite by Cl-rich solutions at temperatures < 320o C. If you start seeing chromite, lizardite, brucite in float, you are in the right ground. Typical habit: platy. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify woodallite?+
Where is woodallite found?+
What rocks look like woodallite?+
What minerals are found with woodallite?+
What kind of rock does woodallite form in?+
What is woodallite used for?+
Find woodallite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
