Keystoneite is an extremely rare copper tellurite mineral typically found as delicate blue crusts or drusy coatings. It is primarily identified in oxidized zones of gold-telluride ore deposits and requires magnification to appreciate its crystal form.
Is this keystoneite?
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 keystoneite with a known reference. Keystoneite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Keystoneite leaves a light blue streak.
- 3Read the lusterHold the specimen under a strong light. Keystoneite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: blue, greenish blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: microcrystalline crusts, drusy coatings.
Often confused with
Keystoneite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside keystoneite
Minerals reported to co-occur with keystoneite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₃TeO₆·2H₂O
- Mohs hardness
- 2-3
- Density
- 3.85 g/cm³
- Colors
- Streak
- Light Blue
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Microcrystalline Crusts, Drusy Coatings
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Tellurium-bearing Hydrothermal Gold Veins
- Typical price
- $100-500+ per specimen depending on size and rarity
Where rockhounds find keystoneite
Classic worldwide localities
- Keystone Mine, Colorado, USA
- Goldfield, Nevada, USA
Field-hunting tip
Look in tellurium-bearing hydrothermal gold veins country, the host setting where keystoneite typically forms. If you start seeing tellurium, coloradoite, quartz in float, you are in the right ground. Field specimens usually show a microcrystalline crusts, drusy coatings habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find keystoneite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
