Keystoneite is a rare magnesium nickel iron oxide, typically golden yellow. It was approved as a distinct mineral species in 1987. It was first described from Keystone mine, Magnolia district, Boulder Co., Colorado, USA.
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 pale yellow-green streak.
- 3Read the lusterHold the specimen under a strong light. Keystoneite typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: golden yellow.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: microcrystalline crusts, drusy coatings.
Often confused with
Keystoneite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Keystoneite leaves pale yellow-green, Chalcomenite leaves pale blue; luster reads adamantine on Keystoneite and vitreous on Chalcomenite.
How to tell apart: Streak differs, so Keystoneite leaves pale yellow-green, Malachite leaves light green; luster reads adamantine on Keystoneite and vitreous on Malachite.
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
- Mg₀.₅NiFe³⁺(Te⁴⁺O₃)₃·4H₂O
- Mohs hardness
- 2-3
- Density
- 4.40 g/cm³
- Colors
- Streak
- Pale Yellow-green
- Luster
- Adamantine
- Transparency
- Translucent
- Crystal system
- Hexagonal
- Crystal habit
- Microcrystalline Crusts, Drusy Coatings
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Tellurium-bearing Hydrothermal Gold Veins
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
How do you identify keystoneite?+
Where is keystoneite found?+
Is keystoneite safe to handle?+
What rocks look like keystoneite?+
What minerals are found with keystoneite?+
What kind of rock does keystoneite form in?+
What is keystoneite used for?+
Find keystoneite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
