Bartonite is a rare potassium-iron sulfide mineral typically found as small, metallic grains within alkaline igneous rocks or evaporite suites. Collectors generally find it as an inclusion or interstitial component, requiring microscopic identification or analytical verification to distinguish from other iron sulfides like pyrrhotite.
Is this bartonite?
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 bartonite with a known reference. Bartonite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: submetallic.
- 4Match the color rangeCompare against the expected color range: black brown.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: massive, granular, or anhedral grains.
Often confused with
Bartonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Bartonite leaves black, Pyrrhotite leaves dark grayish black; luster reads submetallic on Bartonite and metallic on Pyrrhotite.
How to tell apart: Streak differs, so Bartonite leaves black, Pentlandite leaves pale bronze-brown; luster reads submetallic on Bartonite and metallic on Pentlandite.
Often found alongside bartonite
Minerals reported to co-occur with bartonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₆Fe₂₀S₂₆S
- Mohs hardness
- 3.5
- Density
- 3.305 g/cm³
- Colors
- Streak
- Black
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Tetragonal
- Crystal habit
- Massive, granular, or anhedral grains
- Cleavage
- {112}, distinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In clots with other sulfides and silicates in an alkalic diatreme which intruded Franciscan rocks
Where rockhounds find bartonite
Classic worldwide localities
- Coyote Peak, near Orick, Humboldt Co., California, USA (type locality)
Field-hunting tip
Where it forms: In clots with other sulfides and silicates in an alkalic diatreme which intruded Franciscan rocks. If you start seeing rasvumite, djerfisherite, erdite in float, you are in the right ground. Typical habit: massive, granular, or anhedral grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify bartonite?+
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What rocks look like bartonite?+
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Find bartonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
