Bannermanite is an exceptionally rare vanadium oxide mineral found in volcanic fumaroles. It typically occurs as small, black, acicular crystal aggregates and is primarily valued by advanced mineral collectors for its unique geological origin.
Is this bannermanite?
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 bannermanite with a known reference. Bannermanite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Bannermanite leaves a dark gray-black streak.
- 3Read the lusterHold the specimen under a strong light. Bannermanite typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular or fibrous aggregates, small tabular crystals.
Often confused with
Bannermanite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Bannermanite leaves dark gray-black, Vanadinite leaves white; luster reads submetallic on Bannermanite and subadamantine on Vanadinite.
How to tell apart: Streak differs, so Bannermanite leaves dark gray-black, Descloizite leaves orange to brownish-red; luster reads submetallic on Bannermanite and greasy to adamantine on Descloizite.
Often found alongside bannermanite
Minerals reported to co-occur with bannermanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Na,K)V₅O₁₃·nH₂O
- Mohs hardness
- 3-4
- Density
- 3.32 g/cm³
- Colors
- Streak
- Dark Gray-black
- Luster
- Submetallic
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular or Fibrous Aggregates, Small Tabular Crystals
- Cleavage
- {100}, Perfect; {010}, Fair
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Fumarolic Deposits
Where rockhounds find bannermanite
Classic worldwide localities
- Izalco Volcano, El Salvador
Field-hunting tip
Look in fumarolic deposits country, the host setting where bannermanite typically forms. If you start seeing thenardite, blödite, vanadium oxides in float, you are in the right ground. Field specimens usually show a acicular or fibrous aggregates, small tabular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify bannermanite?+
Where is bannermanite found?+
Is bannermanite safe to handle?+
What rocks look like bannermanite?+
What minerals are found with bannermanite?+
What kind of rock does bannermanite form in?+
What is bannermanite used for?+
Find bannermanite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
