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 3-3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Theophrastite leaves a light green streak.
- 3Read the lusterHold the specimen under a strong light. Theophrastite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: emerald-green, grass-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 — Theophrastite leaves light green, Zaratite leaves pale green.
How to tell apart: Bunsenite is the harder of the two (Mohs 5.5 vs. 3-3.5); streak differs — Theophrastite leaves light green, Bunsenite leaves greenish 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
- 3-3.5
- Density
- 3.32 g/cm³
- Colors
- Streak
- Light Green
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Tabular Crystals, Massive, Crusts
- Cleavage
- Perfect On {0001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins in Ultramafic Rocks
- Typical price
- $50-500 depending on crystal size and clarity
Where rockhounds find theophrastite
Classic worldwide localities
- Veria, Greece
- Unst, Shetland Islands, Scotland
- Kambalda, Western Australia
Field-hunting tip
Look in hydrothermal veins in ultramafic rocks country — that is the host setting where theophrastite typically forms. If you start seeing heazlewoodite, magnetite, chromite in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find theophrastite on the map
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