Starkeyite is an unstable, hydrated magnesium sulfate mineral that typically forms as an efflorescent crust in dry environments. It is highly susceptible to dehydration, often altering to hexahydrite or epsomite if exposed to humidity, requiring careful storage in sealed containers to preserve its structural integrity.
Is this starkeyite?
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 starkeyite with a known reference. Starkeyite sits at Mohs 2-2.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Starkeyite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Starkeyite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, pale yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, efflorescent crusts, granular.
Often confused with
Starkeyite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside starkeyite
Minerals reported to co-occur with starkeyite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MgSO₄·4H₂O
- Mohs hardness
- 2-2.5
- Density
- 1.79 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, Efflorescent Crusts, Granular
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Ore Zones of Sulfide Mines
- Typical price
- $10-50 per specimen
Where rockhounds find starkeyite
Classic worldwide localities
- Starkey mine, Montana, USA
- Bolivia
- Germany
- Chile
Field-hunting tip
Look in oxidized ore zones of sulfide mines country — that is the host setting where starkeyite typically forms. If you start seeing epsomite, hexahydrite, gypsum in float, you are in the right ground. Field specimens usually show a fibrous, efflorescent crusts, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify starkeyite?+
Where is starkeyite found?+
How much is starkeyite worth?+
What rocks look like starkeyite?+
What minerals are found with starkeyite?+
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Find starkeyite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
