Theophrastite is a rare nickel hydroxide mineral known for its striking emerald-green color. It typically forms as thin tabular crystals or crusts within serpentinized ultramafic rocks, often associated with other nickel minerals like heazlewoodite.
Is this theophrastite?
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 theophrastite with a known reference. Theophrastite 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. Streak: pale green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: emerald green.
- 5Look at form & habitCrystal system: trigonal. Typical habit: tabular crystals, massive, crusts.
Often confused with
Theophrastite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Theophrastite leaves pale green, Zaratite leaves light green.
How to tell apart: Bunsenite is the harder of the two (Mohs 5.5 vs. 3.5); streak differs, so Theophrastite leaves pale green, Bunsenite leaves brownish black.
Often found alongside theophrastite
Minerals reported to co-occur with theophrastite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ni(OH)₂
- Mohs hardness
- 3.5
- Density
- 4 g/cm³
- Colors
- Streak
- Pale green
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Tabular crystals, massive, crusts
- Cleavage
- {0001}, perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As coatings in chromitite in lenses in serpentinites (Vermion district, Greece); on chromitite (Hagdale quarry, Scotland)
Where rockhounds find theophrastite
Classic worldwide localities
- Verrnion district, 50 km west of Thessalonike, Macedonia, Greece
- Hagdale quarry, Unst, Shetland Islands, Scotland
- Lord Brassey mine, Heazlewood, Tasmania, Australia
Field-hunting tip
Where it forms: As coatings in chromitite in lenses in serpentinites (Vermion district, Greece); on chromitite (Hagdale quarry, Scotland). If you start seeing magnetite, chromite, millerite in float, you are in the right ground. Typical habit: tabular crystals, massive, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify theophrastite?+
Where is theophrastite found?+
Is theophrastite safe to handle?+
What rocks look like theophrastite?+
What minerals are found with theophrastite?+
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Find theophrastite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
