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, so 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, so 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, 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
How do you identify theophrastite?+
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Find theophrastite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
