Utahite is a rare magnesium copper zinc hydroxide, typically pale blue to blue-green. It is associated with cesbronite and quartz. It was first described from the mine dumps of the Centennial Eureka mine, Tintic district, Juab Co., Utah, USA.
Is this utahite?
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 utahite with a known reference. Utahite sits at Mohs ~4-5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale blue.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to pearly.
- 4Match the color rangeCompare against the expected color range: pale blue, greenish blue.
- 5Look at form & habitCrystal system: triclinic. Typical habit: aggregates, prismatic.
Often confused with
Utahite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Utahite is noticeably harder (Mohs ~4-5 vs. 2.5-3); luster reads vitreous to pearly on Utahite and pearly on {010} on Copiapite.
How to tell apart: Luster reads vitreous to pearly on Utahite and subadamantine to vitreous, resinous on fractures on Jarosite.
Often found alongside utahite
Minerals reported to co-occur with utahite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MgCu²⁺₄Zn₂Te⁶⁺₃O₁₄(OH)₄·6H₂O
- Mohs hardness
- ~4-5
- Density
- 5.33 g/cm³
- Colors
- Streak
- Pale blue
- Luster
- Vitreous to pearly
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Aggregates, prismatic
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A very rare secondary mineral found on dump material from the oxidized zone of a Cu–Zn–Te-bearing hydrothermal ore deposit
Where rockhounds find utahite
Classic worldwide localities
- The Centennial Eureka mine, 1 mile southeast of Eureka, Tintic District, Juab County, Utah, USA (type locality)
Field-hunting tip
Where it forms: A very rare secondary mineral found on dump material from the oxidized zone of a Cu–Zn–Te-bearing hydrothermal ore deposit. If you start seeing cesbronite, quartz in float, you are in the right ground. Typical habit: aggregates, prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
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Find utahite on the map
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